Found 77 papers in cond-mat


Search terms: (topolog[a-z]+)|(graphit[a-z]+)|(rhombohedr[a-z]+)|(graphe[a-z]+)|(chalcog[a-z]+)|(landau)|(weyl)|(dirac)|(STM)|(scan[a-z]+ tunne[a-z]+ micr[a-z]+)|(scan[a-z]+ tunne[a-z]+ spectr[a-z]+)|(scan[a-z]+ prob[a-z]+ micr[a-z]+)|(MoS.+\d+|MoS\d+)|(MoSe.+\d+|MoSe\d+)|(MoTe.+\d+|MoTe\d+)|(WS.+\d+|WS\d+)|(WSe.+\d+|WSe\d+)|(WTe.+\d+|WTe\d+)|(Bi\d+Rh\d+I\d+|Bi.+\d+.+Rh.+\d+.+I.+\d+.+)|(BiTeI)|(BiTeBr)|(BiTeCl)|(ZrTe5|ZrTe.+5)|(Pt2HgSe3|Pt.+2HgSe.+3)|(jacuting[a-z]+)|(flatband)|(flat.{1}band)|(LK.{1}99)

Coalescence of sessile aqueous droplets laden with surfactant
S. Arbabi, P. Deuar, R. Bennacer, Z. Che, P. E. Theodorakis
arXiv:2403.10535v1 Announce Type: new Abstract: With most of the focus to date having been on the coalescence of freely suspended droplets, much less is known about the coalescence of sessile droplets, especially in the case of droplets laden with surfactant. Here, we employ large-scale molecular dynamics simulations to investigate this phenomenon on substrates with different wettability. In particular, we unravel the mass transport mechanism of surfactant during coalescence, thus explaining the key mechanisms present in the process. Close similarities are found between the coalescence of sessile droplets with equilibrium contact angles above 90{\deg} and that of freely suspended droplets, being practically the same when the contact angle of the sessile droplets is above 140{\deg}. Here, the initial contact point is an area that creates an initial contact film of surfactant that proceeds to break into engulfed aggregates. A major change in the physics appears below the 90{\deg} contact angle, when the initial contact point becomes small and line-like, strongly affecting many aspects of the process and allowing water to take part in the coalescence from the beginning. We find growth exponents consistent with a 2/3 power law on strongly wettable substrates but no evidence of linear growth. Overall bridge growth speed increases with wettability for all surfactant concentrations, but the speeding up effect becomes weaker as surfactant concentration grows, along with a general slowdown of the coalescence compared to pure water. Concurrently, the duration of the initial thermally limited regime increases strongly by almost an order of magnitude for strongly wettable substrates.

Practical realization of chiral nonlinearity for strong topological protection
Xinxin Guo, Lucien Jezequel, Mathieu Padlewski, Herv\'e Lissek, Pierre Delplace, Romain Fleury
arXiv:2403.10590v1 Announce Type: new Abstract: Nonlinear topology has been much less inquired compared to its linear counterpart. Existing advances have focused on nonlinearities of limited magnitudes and fairly homogeneous types. As such, the realizations have rarely been concerned with the requirements for nonlinearity. Here we explore nonlinear topological protection through the determination of nonlinear rules and demonstrate their relevance in real-world experiments. We take advantage of chiral symmetry and identify the condition for its continuation in general nonlinear environments. Applying it to one-dimensional topological lattices, we can obtain definite evolution paths of zero-energy edge states that preserve topologically nontrivial phases regardless of the specifics of the chiral nonlinearities. Based on an acoustic prototype design, we theoretically, numerically, and experimentally showcase the nonlinear topological edge states that persist in all nonlinear degrees and directions without any frequency shift. Our findings unveil a broad family of nonlinearities that are compatible with topological non-triviality, establishing a solid ground for future drilling in the emergent field of nonlinear topology.

New insights into the origin of the first sharp diffraction peak in amorphous silica from an analysis of chemical and radial ordering
Parthapratim Biswas, Devilal Dahal, Stephen R. Elliott
arXiv:2403.10632v1 Announce Type: new Abstract: The structural origin of the first sharp diffraction peak (FSDP) in amorphous silica is studied by analyzing chemical and radial ordering of silicon (Si) and oxygen (O) atoms in binary amorphous networks. The study shows that the chemical order involving Si--O and O--O pairs play a major role in the formation of the FSDP in amorphous silica. This is supplemented by small contributions arising from the relatively weak Si--Si correlations in the Fourier space. A shell-by-shell analysis of the radial correlations between Si--Si, Si--O and O--O atoms in the network reveals that the position and the intensity of the FSDP are largely determined by atomic pair correlations originating from the first two/three radial shells on a length scale of about 5--8 {\AA}, whereas the fine structure of the intensity curve in the vicinity of the FSDP is perturbatively modified by atomic correlations arising from the radial shells beyond 8 {\AA}. The study leads to a simple mathematical relationship between the position of the radial peaks ($r_k$) in the partial pair-correlation functions and the diffraction peaks ($Q_k$) that can be used to obtain approximate positions of the FSDP and the principal peak. The results are complemented by numerical calculations and an accurate semi-analytical expression for the diffraction intensity obtained from the partial pair-correlation functions of amorphous silica for a given radial shell.

Ion solvation in atomic baths: from snowballs to polarons
Saajid Chowdhury, Jes\'us P\'erez-R\'ios
arXiv:2403.10639v1 Announce Type: new Abstract: Solvation, the result of the complicated interplay between solvent-solute and solvent-internal interactions, is one of the most important chemical processes. Consequently, a complete theoretical understanding of solvation seems a heroic task. However, it is possible to elucidate fundamental solvation mechanisms by looking into simpler systems, such as ion solvation in atomic baths. In this work, we study ion solvation by calculating the ground state properties of a single ion in a neutral bath from the high-density regime to the low-density regime, finding common ground for these two, in principle, disparate regimes. Our results indicate that a single $^{174}$Yb$^+$ ion in a bath of $^{7}$Li atoms forms a coordination complex at high densities with a coordination number of 8, with strong electrostriction, characteristic of the snowball effect. On the contrary, treating the atomic bath as a dilute quantum gas at low densities, we find that the ion-atom interaction's short-range plays a significant role in the physics of many-body bound states and polarons. Furthermore, in this regime, we explore the role of a putative ion trap, which drastically affects the binding mechanism of the ion and atoms from a quantum gas. Therefore, our results give a novel insight into the universality of ion-neutral systems in the ultracold regime and the possibilities of observing exotic many-body effects.

X-ray Nano-imaging of a Heterogeneous Structural Phase Transition in V2O3
Ziming Shao, Aileen Luo, Eti Barazani, Tao Zhou, Zhonghou Cai, Martin V. Holt, Yoav Kalcheim, Andrej Singer
arXiv:2403.10719v1 Announce Type: new Abstract: Controlling the Mott transition through strain engineering is crucial for advancing the development and application of memristive and neuromorphic computing devices. Yet, Mott insulators are heterogeneous due to intrinsic phase boundaries and extrinsic defects, posing significant challenges to fully understanding the impact of local microscopic distortions on the local Mott transition, which demands structural characterizations at the relevant length scale. Here, using a synchrotron-based scanning X-ray nanoprobe, we studied the real-space structural heterogeneity during the structural phase transition in a V2O3 thin film, with a resolution of 30 nm. Through temperature-dependent metal-insulator phase coexistence mapping, we report a variation in the local transition temperature of up to 7 K across the film and the presence of the transition hysteresis at the nanoscale. Furthermore, a detailed quantitative analysis demonstrates that the spatial heterogeneity of the transition is closely tied to the tilting of crystallographic planes in the pure insulating phase. We develop a structural model allowing us to interpret these tilts as variation of the monoclinic distortion during the rhombohedral-monoclinic phase transition. Our work highlights the impact of local heterogeneous lattice distortions on the Mott transition and lays the groundwork for future innovations in harnessing strain heterogeneity within Mott systems for the next-generation computational technologies.

Bifurcations of inflating balloons and interacting hysterons
Gentian Muhaxheri, Christian D. Santangelo
arXiv:2403.10721v1 Announce Type: new Abstract: While many materials exhibit a complex, hysteretic response to external driving, there has been a surge of interest in how the complex dynamics of internal materials states can be understood and designed to process and store information. We consider a system of connected rubber balloons that can be described by a Preisach model of non-interacting hysterons under pressure control, but for which the hysterons become coupled under volume control. We study this system by exploring the possible transition graphs, as well as by introducing a configuration space approach which tracks the volumes of each balloon. Changes in the transition graphs turn out to be related to changes in the topology of the configuration space of the balloons, providing a particularly geometric view of how transition graphs can be designed, as well as additional information on the existence of hidden metastable states. This class of systems is more general than just balloons.

Emergent $D_8^{(1)}$ spectrum and topological soliton excitation in CoNb$_2$O$_6$
Ning Xi, Xiao Wang, Yunjing Gao, Yunfeng Jiang, Rong Yu, Jianda Wu
arXiv:2403.10785v1 Announce Type: new Abstract: Quantum integrability emerging near a quantum critical point (QCP) is manifested by exotic excitation spectrum that is organized by the associated algebraic structure. A well known example is the emergent $E_8$ integrability near the QCP of a transverse field Ising chain (TFIC), which was long predicted theoretically and initially proposed to be realized in the quasi-one-dimensional (q1D) quantum magnet CoNb$_2$O$_6$. However, later measurements on the spin excitation spectrum of this material revealed a series of satellite peaks that cannot be described by the $E_8$ Lie algebra. Motivated by these experimental progresses, we hereby revisit the spin excitations of CoNb$_2$O$_6$ by combining numerical calculation and analytical analysis. We show that, as effects of strong interchain fluctuations, the spectrum of the system near the 1D QCP is characterized by the $D_{8}^{(1)}$ Lie algebra with robust topological soliton excitation. We further show that the $D_{8}^{(1)}$ spectrum can be realized in a broad class of interacting quantum systems. Our results advance the exploration of integrability and manipulation of topological excitations in quantum critical systems.

Orbital magnetic susceptibility of circular graphene nanoribbons studied using tight-binding model
Norio Inui
arXiv:2403.10818v1 Announce Type: new Abstract: The magnetic properties of a circular graphene nanoribbon (carbon belt) in a magnetic field parallel to its central axis is studied using a tight-binding model. Orbital magnetic susceptibility is calculated using an analytical expression of the energy eigenvalues as a function of the magnetic flux density for any size, and its temperature dependence is considered. In the absence of electron hopping parallel to the magnetic field, the orbital magnetic susceptibility diverges at absolute zero if the chemical potential is zero and the number of atoms is a multiple of four. As the temperature increases, the magnitude of susceptibility decreases according to the power law, whose exponent depends on the size. In the presence of electron hopping parallel to the magnetic field, the divergence of the susceptibility near absolute zero disappears, and the sign changes with the transfer integral parallel to the magnetic field and the temperature.

Ultrafast carriers' separation imaging in WS2-WSe2 in plane heterojunction by transient reflectivity microscopy
Yangguang Zhong, Shuai Yue, Huawei Liu, Yuexing Xia, Anlian Pan, Shula Chen, Xinfeng Liu
arXiv:2403.10848v1 Announce Type: new Abstract: Carrier transport in nanodevices plays a crucial role in determining their functionality. In the post-Moore era, the behavior of carriers near surface or interface domains the function of the whole devices. However, the femtosecond dynamics and nanometer-scale movement of carriers pose challenges for imaging their behavior. Techniques with high spatial-temporal resolution become imperative for tracking their intricate dynamics. In this study, we employed transient reflectivity microscopy to directly visualize the charge separation in the atomic interface of WS2-WSe2 in-plane heterojunctions. The carriers' drifting behavior was carefully tracked, enabling the extraction of drift velocities of 30 nm/ps and 10.6 nm/ps for electrons and holes. Additionally, the width of the depletion layer was determined to be 300 nm based on the carriers' moving trajectory. This work provides essential parameters for the potential effective utilization of these covalent in-plane heterojunctions,and demonstrates the success of transient optical imaging in unraveling the electrical behavior of nano devices, paving the way for a new avenue of electro-optical analysis.

An ab-initio theory of inelastic electron tunneling spectrum of vibrating magnetic molecules adsorbed on superconductors
Athanasios Koliogiorgos, Richard Koryt\'ar
arXiv:2403.10852v1 Announce Type: new Abstract: We present an efficient method of calculating the vibrational spectrum of a magnetic molecule adsorbed on a superconductor, directly related to the first derivative of the tunneling $IV$ curve. The work is motivated by a recent scanning-tunneling spectroscopy of lead phthalocyanine on superconducting Pb(100), showing a wealth of vibrational excitations, the number of which highly exceeds molecular vibrations typically encountered on normal metals. We design a minimal model which represents the inelastic transitions by the spectral function of a frontier orbital of the molecule in isolation. The model allows for an exact solution; otherwise the full correlated superconducting problem would be hard to treat. The model parameters are supplied from an ab-initio calculation, where the presence of the surface on the deformation of molecular geometry can be taken into account. The spectral function of the highest-occupied molecular orbital of the anionic PbPc$^{1-}$ shows the best agreement with the experimental reference among other molecular charge states and orbitals. The method allows to include multiple vibrational transitions straightforwardly.

A simple and accurate method to determine fluid-crystal phase boundaries from direct coexistence simulations
Frank Smallenburg, Giovanni Del Monte, Marjolein de Jager, Laura Filion
arXiv:2403.10891v1 Announce Type: new Abstract: One method for computationally determining phase boundaries is to explicitly simulate a direct coexistence between the two phases of interest. Although this approach works very well for fluid-fluid coexistences, it is often considered to be less useful for fluid-crystal transitions, as additional care must be taken to prevent the simulation boundaries from imposing unwanted strains on the crystal phase. Here, we present a simple adaptation to the direct coexistence method that nonetheless allows us to obtain highly accurate predictions of fluid-crystal coexistence conditions. We test our approach on hard spheres, the screened Coulomb potential, and a 2D patchy-particle model. In all cases, we find excellent agreement between the direct coexistence approach and (much more cumbersome) free-energy calculation methods. Moreover, the method is sufficiently accurate to resolve the (tiny) free-energy difference between the face-centered cubic and hexagonally close-packed crystal of hard spheres in the thermodynamic limit. The simplicity of this method also ensures that it can be trivially implemented in essentially any simulation method or package. Hence, this approach provides an excellent alternative to free-energy based methods for the precise determination of phase boundaries.

Role of Coulomb Interaction in Valley Photogalvanic Effect
V. M. Kovalev, A. V. Parafilo, O. V. Kibis, I. G. Savenko
arXiv:2403.10898v1 Announce Type: new Abstract: We develop a theory of Coulomb interaction-related contribution to the photogalvanic current of electrons in two-dimensional non-centrosymmetric Dirac materials possessing a nontrivial structure of valleys and exposed to an external electromagnetic field. The valley photogalvanic effect occurs here due to the trigonal warping of electrons and holes' dispersions in a given valley of the monolayer. We study the low-frequency limit of the external field: the field frequency is smaller than the temperature $T$, and the electron-electron and electron-hole scattering times are much larger than the electron-impurity scattering time. In this regime, we employ the Boltzmann transport equations and show that electron-hole scattering dominates electron-electron scattering in intrinsic semiconductors. Coulomb interaction-related contribution to the valley photogalvanic current can reduce the value of the bare photogalvanic current as these two currents flow in opposite directions.

Splay-bend elastic inequalities shape tactoids, toroids, umbilics, and conic section walls in paraelectric, twist-bend, and ferroelectric nematics
Oleg D. Lavrentovich
arXiv:2403.10972v1 Announce Type: new Abstract: Elastic constants of splay K_11, twist K_22, and bend K_33 of nematic liquid crystals are often assumed to be equal to each other in order to simplify the theoretical description of complex director fields. Here we present examples of how the disparity of K_11 and K_33 produces effects that cannot be described in a one-constant approximation. In a lyotropic chromonic liquid crystal, nematic droplets coexisting with the isotropic phase change their shape from a simply-connected tactoid to a topologically distinct toroid as a result of temperature or concentration variation. The transformation is caused by the increase of the splay-to-bend ratio K_11/K_33. A phase transition from a conventional nematic to a twist-bend nematic implies that the ratio K_11/K_33 changes from very large to very small. As a result, the defects caused by an externally applied electric field change the deformation mode of optic axis from bend to splay. In the paraelectric-ferroelectric nematic transition, one finds an inverse situation: K_11/K_33 changes from small to large, which shapes the domain walls in the spontaneous electric polarization field as conic sections. The polarization field tends to be solenoidal, or divergence-free, a behavior complementary to irrotational curl-free director textures of a smectic A.

Emergent Haldane Model and Photon-Valley Locking in Chiral Cavities
Liu Yang, Qing-Dong Jiang
arXiv:2403.11063v1 Announce Type: new Abstract: The realization of Haldane's topological graphene model in practical materials has presented significant challenges. Here, we propose achieving this model by embedding graphene in chiral cavities, using the asymptotically decoupled framework detailed in Ref. [Phys. Rev. Lett. 126, 153603 (2021)]. Additionally, we introduce an equilibrium strategy for achieving valley polarization in this system with C2-symmetry breaking. Through numerical methods, we quantify the locking of photon numbers with Bloch electrons and calculate the topology-induced imbalance of valley photons. Furthermore, we elucidate that topological phase transition is characterized by the sign change of photon numbers during interband excitation. These findings underscore the remarkable potential of utilizing cavity quantum fluctuations to engineer electronic and photonic properties specific to valleys and topologies, particularly within the realm of strong light-matter coupling.

Tunable Current Rectification Through a Designer Graphene Nanoribbon
Niklas Friedrich, Jingcheng Li, Iago Pozo, Diego Pe\~na, Jos\'e Ignacio Pascual
arXiv:2403.11132v1 Announce Type: new Abstract: Unimolecular current rectifiers are fundamental building blocks in organic electronics. Rectifying behavior has been identified in numerous organic systems due to electron-hole asymmetries of orbital levels interfaced by a metal electrode. As a consequence, the rectifying ratio (RR) determining the diode efficiency remains fixed for a chosen molecule-metal interface. Here, we present a mechanically tunable molecular diode exhibiting an exceptionally large rectification ratio (>10^5) and reversible direction. The molecular system comprises a 7-armchair graphene nanoribbon (GNR) doped with a single unit of substitutional diboron within its structure, synthesized with atomic precision on a gold substrate by on-surface synthesis. The diboron unit creates half-populated in-gap bound states and splits the GNR frontier bands into two segments, localizing the bound state in a double barrier configuration. By suspending these GNRs freely between the tip of a low-temperature scanning tunneling microscope and the substrate, we demonstrate unipolar hole transport through the boron in-gap state's resonance. Strong current rectification is observed, associated with the varying widths of the two barriers, which can be tuned by altering the distance between tip and substrate. This study introduces an innovative approach for the precise manipulation of molecular electronic functionalities, opening new avenues for advanced applications in organic electronics.

Electrically controlled nonvolatile switching of single-atom magnetism in a Dy@C84 single-molecule transistor
Feng Wang, Wangqiang Shen, Yuan Shui, Jun Chen, Huaiqiang Wang, Rui Wang, Yuyuan Qin, Xuefeng Wang, Jianguo Wan, Minhao Zhang, Xing Lu, Tao Yang, Fengqi Song
arXiv:2403.11137v1 Announce Type: new Abstract: Single-atom magnetism switching is a key technique towards the ultimate data storage density of computer hard disks and has been conceptually realized by leveraging the spin bistability of a magnetic atom under a scanning tunnelling microscope. However, it has rarely been applied to solid-state transistors, an advancement that would be highly desirable for enabling various applications. Here, we demonstrate realization of the electrically controlled Zeeman effect in Dy@C84 single-molecule transistors, thus revealing a transition in the magnetic moment from 3.8 {\mu}B to 5.1 {\mu}B for the ground-state GN at an electric field strength of 3-10 MV/cm. The consequent magnetoresistance significantly increases from 600% to 1100% at the resonant tunneling point. Density functional theory calculations further corroborate our realization of nonvolatile switching of single-atom magnetism, and the switching stability emanates from an energy barrier of 92 meV for atomic relaxation. These results highlight the potential of using endohedral metallofullerenes for high-temperature, high-stability, high-speed, and compact single-atom magnetic data storage.

Theoretical investigation of the vertical dielectric screening dependence on defects for few-layered van der Waals materials
Amit Singh, Seunghan Lee, Hyeonhu Bae, Jahyun Koo, Li Yang, Hoonkyung Lee
arXiv:2403.11140v1 Announce Type: new Abstract: First-principle calculations were employed to analyze the effects induced by vacancies of molybdenum (Mo) and sulfur (S) on the dielectric properties of few-layered MoS2. We explored the combined effects of vacancies and dipole interactions on the dielectric properties of few-layered MoS2. In the presence of dielectric screening, we investigated uniformly distributed Mo and S vacancies, and then considered the case of concentrated vacancies. Our results show that the dielectric screening remarkably depends on the distribution of vacancies owing to the polarization induced by the vacancies and on the interlayer distances. This conclusion was validated for a wide range of wide-gap semiconductors with different positions and distributions of vacancies, providing an effective and reliable method for calculating and predicting electrostatic screening of dimensionally reduced materials. We further provided a method for engineering the dielectric constant by changing the interlayer distance, tuning the number of vacancies and the distribution of vacancies in few-layered van der Waals materials for their application in nanodevices and supercapacitors.

Metal-semiconductor behavior along the line of stacking order change in gated multilayer graphene
W{\l}odzimierz Jask\'olski
arXiv:2403.11143v1 Announce Type: new Abstract: We investigate gated multilayer graphene with stacking order change along the armchair direction. We consider some layers cracked to release shear strain at the stacking domain wall. The energy cones of graphene overlap along the corresponding direction in the k-space, so the topological gapless states from different valleys also overlap. However, these states strongly interact and split due to atomic-scale defects caused by the broken layers, yielding an effective energy gap. We find that for some gate voltages, the gap states cross and the metallic behavior along the stacking domain wall can be restored. In particular cases, a flat band appears at the Fermi energy. We show that for small variations of the gate voltage the charge occupying this band oscillates between the outer layers.

Merons and magnetoelectric switching in centrosymmetric spiral magnets
Luca Maranzana, Naoto Nagaosa, Sergey Artyukhin
arXiv:2403.11195v1 Announce Type: new Abstract: Spiral multiferroics exhibit a strong coupling between magnetic and ferroelectric orders, allowing cross-control. Since the seminal work of Kimura et al. in 2003, these materials have attracted great interest galvanized by the prospect of new high-efficiency memory devices, where magnetic (electric) bits are switched via an external electric (magnetic) field. Nevertheless, the mechanism underlying such a switching process - the electric field-driven dynamics of domain walls (DWs) - is still poorly understood. We address this problem for meron DWs, which represent one of the main DW types in spiral multiferroics and consist of an array of meron (half-skyrmion) strings. Minimum energy walls feature merons with alternating topological charges and move as relativistic massive particles, with the limiting velocity set by magnon speed. Low-energy defects in this alternating charge sequence, which appear during domain nucleation, can lead to DWs with net topological charge. This induces a peculiar non-local dynamics where all the spins in the system rotate, merons translate within the wall, and the DW mobility is suppressed. The topological charge of the wall and the meron helicity can be easily modified via an external magnetic and electric field, respectively, offering fine control over DW dynamics. Defects within the meron strings, analogous to Bloch points, have hedgehog-like spin texture and are strongly pinned to the lattice. The fascinating interplay between domain wall motion, translation of merons within the wall, and precession of spins in the entire domains opens a new playground for the electric manipulation of topological spin textures.

An exact formula for the optical conductivity of the two dimensional Hubbard model and its application to the cuprate superconductors
Xinyue Liu, Tao Li
arXiv:2403.11224v1 Announce Type: new Abstract: Understanding the origin of electron incoherence is believed to be the first step toward the resolution of the mysteries of the high-T$_{c}$ cuprate superconductors. Such electron incoherence manifests itself most evidently in the non-Drude form of the optical absorption spectrum of the system. The spectral weight transfer related to such dissipative response, which is absent in conventional Fermi liquid metal, has direct consequence on the dc transport property of the system. However, a theoretical study of the optical conductivity of a strongly correlated model is a formidable task. Here we present an exact formula for the optical conductivity of the 2D Hubbard model from the low energy effective theory perspective. We show that the optical conductivity in Matsubara frequency of the 2D Hubbard model can be represented as the ensemble average of the optical conductivity of non-interacting systems in the background of fluctuating local moment. We find that such an ensemble average can be done exactly with a sign-problem-free Monte Carlo simulation if we assume the widely adopted Millis-Monien-Pines spin susceptibility for the fluctuating local moment. For thermal fluctuation of the local moment, our formula can be used to calculate directly the optical conductivity in real frequency which can be compared with the result of optical measurements in the cuprate superconductors.

Observation of unconventional charge order during the transition from Mott-insulator to charge-transfer-insulator in $\alpha$-RuCl$_3$
Xiaohu Zheng, Zhengxin Liu, Cuiwei Zhang, Huaxue Zhou, Chongli Yang, Youguo Shi, Katsumi Tanigaki, Rui-Rui Du
arXiv:2403.11232v1 Announce Type: new Abstract: The magnetic nature of the Kitaev candidate material $\alpha$-RuCl$_3$ has been widely studied but its charge properties are less known. In the present work, we systematically investigate the scanning tunneling microscopy/spectroscopy (STM/STS) on few-layer $\alpha$-RuCl$_3$ in proximity to graphite. While a single-layer $\alpha$-RuCl$_3$ has a large Mott gap of order 2 eV in spite of charge transferring to the heterointerface from graphite, surface of 2-monolayers (MLs) and 3-MLs samples have a reduced charge gap of order of 200 meV. Furthermore, clear signals of lattice and charge incommensurate super-modulations are observed in 2-MLs $\alpha$-RuCl$_3$ with negative sample biases outside the charge gap. The dI/dV spectra indicates that 2-MLs and 3-MLs $\alpha$-RuCl$_3$ are turned from Mott insulator into charge transfer insulator, while the charge super-modulation suggests the existence of charge density wave induced by incommensurate dipole order.

Resistive and ballistic phonon transport in $\beta$-Ga$_2$O$_3$
R. Ahrling, R. Mitdank, A. Popp, J. Rehm, A. Akhtar, Z. Galazka, S. F. Fischer
arXiv:2403.11341v1 Announce Type: new Abstract: The anisotropic thermal conductivity and the phonon mean free path (mfp) in monoclinic $\beta$-Ga$_2$O$_3$ single crystals and homoepitaxial films of several $\mu$m were determined using the 3$\omega$-method in the temperature range from 10K-300 K. The measured effective thermal conductivity of both, single crystal and homoepitaxial films are in the order of 20 W/(mK) at room temperature, below 30 K it increases with a maximum of 1000 to 2000 W/(mK) and decreases with T$^3$ below 25 K. Analysis of the phonon mfp shows a dominance of phonon-phonon-Umklapp scattering above 80 K, below which the influence of point-defect scattering is observed. Below 30 K the phonon mfp increases until it is limited by the total $\beta$-Ga$_2$O$_3$ sample size. A crossover from resistive to ballistic phonon transport is observed below 20 K and boundary effects of the total sample size become dominant. This reveals that the homoepitaxial film-substrate interface is highly phonon-transparent. The resistive and ballistic phonon transport regimes in $\beta$-Ga$_2$O$_3$ are discussed corresponding to the models of Callaway and Majumdar, respectively.

Performance of graphene Hall effect sensors: role of bias current, disorder and Fermi velocity
Lionel Petit, Tom Fournier, G\'eraldine Ballon, C\'edric Robert, Delphine Lagarde, Pascal Puech, Thomas Blon, Benjamin Lassagne
arXiv:2403.11342v1 Announce Type: new Abstract: Graphene Hall effect magnetic field sensors hold great promise for the development of ultra-sensitive magnetometers. Their performance is frequently analysed using the two-channel model where electron and hole conductivities are simply added. Unfortunately, this model is unable to capture all the features of the sensor, particularly the bias current dependence of the magnetic field sensitivity. Here we present an advanced model that provides an in-depth understanding of how graphene Hall sensors operate, and demonstrate its ability to quantitatively assess their performance. First, we report the fabrication of sensors with different qualities of graphene, with the best devices achieving magnetic field sensitivities as high as 5000 ohms/T, outperforming the best silicon and narrow-gap semiconductor-based sensors. Then, we examine their performance in detail using the proposed numerical model, which combines Boltzmann formalism, with distinct Fermi levels for electrons and holes, and a new method for the introduction of substrate-induced electron-hole puddles. Importantly, the dependences of magnetic field sensitivity on bias current, disorder, substrate and Hall bar geometry are quantitatively reproduced for the first time. In addition, the model emphasizes that the performance of devices with widths of the order of the charge carrier diffusion length, is significantly affected by the bias current due to the occurrence of large and non-symmetric carrier accumulation and depletion areas near the edges of the Hall bar. The formation of these areas induces a transverse diffusion particle flux capable of counterbalancing the particle flux induced by the Lorentz force when the Hall electric field cancels out in the ambipolar regime. Finally, we discuss how sensor performance can be enhanced by Fermi velocity engineering, paving the way for future ultra-sensitive graphene Hall effect sensors.

Exclusive interplay between topological quasiparticles and strongly correlated fermions
Byungkyun Kang, Zachary Brown, Myoung-Hwan Kim, Hyunsoo Kim, Chul Hong Park
arXiv:2403.11382v1 Announce Type: new Abstract: The low-energy excitations of topological quantum matter have been increasingly comprehended. However, the impact of these excitations on strongly correlated fermions remains rarely explored. Here, we report the discovery of an incompatible dynamic of 4$f$ quasiparticle and topological quasiparticle. The former forms through screening processes, while the latter suppresses the screening channel. By employing ab initio many-body perturbation theory combined with dynamical mean field theory, we show that this effect prompts two types of topological semimetals. The type-I semimetal PrPtBi exhibits a topological quasiparticle away from the Fermi level due to the formation of a 4$f$ quasiparticle. The type-II semimetals HoPtBi and PrAlGe feature a robust topological quasiparticle at the Fermi level, which pushes the 4$f$ quasiparticle away. Our work provides an avenue to harness semimetals' anomalous quantum effects from topological quasiparticle to heavy-fermion behavior by the incorporation of 4$f$ quasiparticles.

Antiferromagnetic Ground State, Charge Density Waves and Oxygen Vacancies Induced Metal-Insulator Transition in Pressurized La$_{3}$Ni$_{2}$O$_{7}$
Xin-Wei Yi, Ying Meng, Jia-Wen Li, Zheng-Wei Liao, Jing-Yang You, Bo Gu, Gang Su
arXiv:2403.11455v1 Announce Type: new Abstract: La$_{3}$Ni$_{2}$O$_{7}$ has garnered widespread interest recently due to its high-temperature superconductivity under pressure, accompanied by charge density wave (CDW) ordering and metal-insulator (MI) transitions in the phase diagram. Here, we reveal with comprehensive calculations that La$_{3}$Ni$_{2}$O$_{7}$ possesses an antiferromagnetic ground state under both low and high pressures, with the strong Fermi surface nesting contributed by the flat band that leads to phonon softening and electronic instabilities. Several stable CDW orders with oxygen octahedral distortions are identified, which can trigger the MI transitions. The estimated CDW transition temperature ($\approx$120 K) at ambient pressure agrees nicely with experimental results. In the presence of apical oxygen vacancies, we identify two different phases, say, half distortion and full distortion phases, respectively, and their competition can lead to a pressure-induced MI transition, in good agreement with experimental observations. In addition, we find that the electron-phonon coupling is too small to contribute to superconductivity. These results appear to indicate an unconventional superconducting pairing mechanism mediated by antiferromagnetic fluctuations. A phase diagram that is consistent with the experimental results is given. The present results not only explain the origins of experimentally observed CDW and MI transitions, but also provide insight for deeply understanding the properties like superconductivity, CDW and the role of oxygen vacancies in pressurized La$_{3}$Ni$_{2}$O$_{7}$.

Ultra-Long Homochiral Graphene Nanoribbons Grown Within h-BN Stacks for High-Performance Electronics
Bosai Lyu, Jiajun Chen, Sen Wang, Shuo Lou, Peiyue Shen, Jingxu Xie, Lu Qiu, Izaac Mitchell, Can Li, Cheng Hu, Xianliang Zhou, Kenji Watanabe, Takashi Taniguchi, Xiaoqun Wang, Jinfeng Jia, Qi Liang, Guorui Chen, Tingxin Li, Shiyong Wang, Wengen Ouyang, Oded Hod, Feng Ding, Michael Urbakh, Zhiwen Shi
arXiv:2403.11465v1 Announce Type: new Abstract: Van der Waals encapsulation of two-dimensional materials within hexagonal boron nitride (h-BN) stacks has proven to be a promising way to create ultrahigh-performance electronic devices. However, contemporary approaches for achieving van der Waals encapsulation, which involve artificial layer stacking using mechanical transfer techniques, are difficult to control, prone to contamination, and unscalable. Here, we report on the transfer-free direct growth of high-quality graphene nanoribbons (GNRs) within h-BN stacks. The as-grown embedded GNRs exhibit highly desirable features being ultralong (up to 0.25 mm), ultranarrow ( < 5 nm), and homochiral with zigzag edges. Our atomistic simulations reveal that the mechanism underlying the embedded growth involves ultralow GNR friction when sliding between AA'-stacked h-BN layers. Using the grown structures, we demonstrate the transfer-free fabrication of embedded GNR field-effect devices that exhibit excellent performance at room temperature with mobilities of up to 4,600 $cm^{2} V^{-1} s^{-1}$ and on-off ratios of up to $10^{6}$. This paves the way to the bottom-up fabrication of high-performance electronic devices based on embedded layered materials.

Moore-Read state in Half-filled Moir\'e Chern band from three-body Pseudo-potential
Lu Zhang, Xue-Yang Song
arXiv:2403.11478v1 Announce Type: new Abstract: The moir\'e system provides a tunable platform for exploring exotic phases of materials. This article shows the possible realization of a non-Abelian state characterized by the Moore-Read wavefunction in a half-filled moir\'e Chern band, exemplified by twisted $\rm MoTe_2$. This is achieved by introducing short-range repulsive three-body interaction. Exact diagonalization is employed to examine the spectrum in finite size. The incompressibility of the system, the degeneracy of the ground states, and the number of low-energy states provide compelling evidence to identify the ground state as the Moore-Read state. We further interpolate between the three-body interaction and Coulomb interaction to show a phase transition between the composite Fermi-liquid and the Moore-Read state. Finally, we consider the effect of band mixing and derive the three-body interaction using perturbation theory. By exploring the conditions under which band mixing effects mimic short-range repulsive three-body interaction we provide insights towards realizing non-Abelian phases of matter in the moir\'e system.

Optical manipulation of the topological phase in ZrTe5 revealed by time- and angle-resolved photoemission
Chaozhi Huang, Chengyang Xu, Fengfeng Zhu, Shaofeng Duan, Jianzhe Liu, Lingxiao Gu, Shichong Wang, Haoran Liu, Dong Qian, Weidong Luo, Wentao Zhang
arXiv:2403.11518v1 Announce Type: new Abstract: High-resolution time- and angle-resolved photoemission measurements were conducted on the topological insulator ZrTe5. With strong femtosecond photoexcitation, a possible ultrafast phase transition from a weak to a strong topological insulating phase was experimentally realized by recovering the energy gap inversion in a time scale that was shorter than 0.15 ps. This photoinduced transient strong topological phase can last longer than 2 ps at the highest excitation fluence studied, and it cannot be attributed to the photoinduced heating of electrons or modification of the conduction band filling. Additionally, the measured unoccupied electronic states are consistent with the first-principles calculation based on experimental crystal lattice constants, which favor a strong topological insulating phase. These findings provide new insights into the longstanding controversy about the strong and weak topological properties in ZrTe5, and they suggest that many-body effects including electron-electron interactions must be taken into account to understand the equilibrium weak topological insulating phase in ZrTe5.

The effect of Coulomb assisted hopping on STM signal: extended two site Hubbard model analysis
Garry Goldstein
arXiv:2403.11566v1 Announce Type: new Abstract: In this work we study STM signal in the presence of Coulomb assisted hopping. We perform an extended two site Hubbard model analysis between the atom on the tip and the atom in the sample nearest to each other. We show that in the presence of Coulomb assisted hopping the STM signal depends on several spectral functions thereby complicating its interpretation. Furthermore in the broadband tip limit there are now three different competing rates for the total current (instead of one for the usual two site Hubbard model analysis). We find an exact (within the Fermi golden rule - that is in the limit of weak coupling between tip and sample) an expression for the current as a function of the bias voltage. As an example we apply our calculations to the case of free fermions with a uniform density of states. Even in this simple case there are non-trivial corrections where the dI/dV (the rate of change of the current with respect to bias voltage) is not uniform as a two site (non-extended) Hubbard model analysis would predict.

Fractional Dimensional Approach to Dielectric Tuning Effects on Excitonic Parameters in 2D semiconductor materials
Lakshminarayan Sharma, Carlos Rodriguez-Fernandez, Humeyra Caglayan
arXiv:2403.11579v1 Announce Type: new Abstract: We demonstrated the potential of the fractional dimensional approach to understand exciton parameters in the exemplary atomically thin semiconductor material, a monolayer of WS$_2$. This approach has proved to be successful in finding the exciton binding energy and quasiparticle bandgap for the WS$_2$ monolayer in varying dielectric environments. A tuning of the quasiparticle bandgap and binding energy by 141 meV and 188 meV, respectively, has been achieved by varying the dielectric of the environment from 1.52 to 8.1. The approach is justified by comparing the changes in the binding energy with the computational results from the Quantum Electrostatic Heterostructures model. The fractional dimension found through the excitonic Rydberg series is close to 2.8 for WS$_2$ monolayer in all different dielectric surroundings. Thus, this approach provides a rapid and robust method for determining the binding energy of excitons in 2D semiconductors independent of the particular dielectric environment.

Investigation of magnetic order influenced phonon and electron dynamics in MnBi$_{2}$Te$_{4}$ and Sb doped MnBi$_{2}$Te$_{4}$ through terahertz time-domain spectroscopy
Soumya Mukherjee, Anjan Kumar NM, Subhadip Manna, Sambhu G Nath, Radha Krishna Gopal, Chiranjib Mitra, N. Kamaraju
arXiv:2403.11580v1 Announce Type: new Abstract: MnBi$_{2}$Te$_{4}$, the first topological insulator with inherent magnetic ordering, has attracted significant attention recently for providing a platform to realize several exotic quantum phenomena at relatively higher temperatures. In this work, we have carried out an exhaustive investigation of MnBi$_{2}$Te$_{4}$ and Sb doped MnBi$_{2}$Te$_{4}$ thin films using THz time-domain spectroscopy. The extracted real THz conductivity displays a strong IR active E$_u$ phonon absorption peak (at $\sim$1.5 THz) merged on top of the Drude-like contributions from bulk and surface electrons. The extracted parameters from the THz conductivity data fitted to the Drude-Fano-Lorentz model, show significant changes in their temperature dependence around the magnetic ordering N\'eel temperature of $\sim$ 25K, which is suggestive of the coupling between magnetic ordering and electronic band structure. The frequency of the E$_u$ phonon displays an anomalous blue-shift with increasing temperatures by $\sim$ 0.1 THz ($\sim$7 %) for MnBi$_{2}$Te$_{4}$ and $\sim$0.2 THz ($\sim$13 %) for Sb doped MnBi$_{2}$Te$_{4}$ between 7K and 250K. The line-shape of the E$_u$ phonon mode in Sb doped MnBi$_{2}$Te$_{4}$ shows significant Fano asymmetry compared to that of MnBi$_{2}$Te$_{4}$, indicating that Sb doping plays an important role in the Fano interference between the phonons and the electrons, in this system. These results indicate that the anomalous phonon behaviour seen in MBT arise mainly from positive cubic anharmonicity induced self energy parameter, whereas both anharmonicity and the electron phonon coupling are at play in making the relatively higher anomalous blue shift of phonons in MBST. Our studies provide the first comprehensive understanding of the phonon and electron dynamics of MnBi$_{2}$Te$_{4}$ and Sb doped MnBi$_{2}$Te$_{4}$ in the THz range using time-domain THz spectroscopy.

Laser Annealed Two Dimensional SiO2/Si1-xGex Scaffolds for Nanoscaled Devices, Synergy of Experiment and Computation
Damiano Ricciarelli, Jonas M\"uller, Guilhem Larrieu, Ioannis Deretzis, Gaetano Calogero, Enrico Martello, Giuseppe Fisicaro, Jean-Michel Hartmann, S\'ebastien Kerdil\`es, Mathieu Opprecht, Antonio Massimiliano Mio, Richard Daubriac, Fuccio Cristiano, Antonino La Magna
arXiv:2403.11606v1 Announce Type: new Abstract: Ultraviolet nanosecond laser annealing (UV-NLA) proves to be an important technique, particularly when tightly controlled heating and melting are necessary. In the realm of semiconductor technologies, the significance of laser annealing (NLA) grows in tandem with the escalating intricacy of integration schemes in nano-scaled devices. Silicon-germanium alloys have been studied for decades for their compatibility with silicon devices. Indeed, they enable the manipulation of properties like strain, carrier mobilities and bandgap. Laser melting on such type of layers, however results, up to now, in the development of extended defects and poor control over layer morphology. In our study, we investigate the laser melting of ~700 nm thick relaxed silicon-germanium samples coated with SiO2 nano-arrays, achieving a precise control of the melting process, without observing the formation of extended defects at the interface left by the liquid front. We found the geometrical parameters of the silicon oxide having an impact on the thermal budget samples see, influencing melt threshold, melt depth and germanium distribution.

SU(3) gauge field of magnons in antiferromagnetic skyrmion crystals
Masataka Kawano
arXiv:2403.11655v1 Announce Type: new Abstract: Quasiparticle excitations in material solids often experience a fictitious gauge field, which can be a potential source of intriguing transport phenomena. Here, we show that low-energy excitations in insulating antiferromagnetic skyrmion crystals on the triangular lattice are effectively described by magnons with an SU(3) gauge field. The three-sublattice structure in the antiferromagnetic skyrmion crystals is inherited as three internal degrees of freedom for the magnons, which are coupled with their kinetic motion via the SU(3) gauge field that arises from the topologically nontrivial spin texture in real space. We also demonstrate that the non-commutativity of the SU(3) gauge field breaks an effective time-reversal symmetry and contributes to a magnon thermal Hall effect.

Tailoring topological band properties of twisted double bilayer graphene: effects due to spin-orbit coupling
Kamalesh Bera, Priyanka Mohan, Arijit Saha
arXiv:2403.11660v1 Announce Type: new Abstract: Our theoretical study unfolds the topological phase transitions (within bands of the Moir\'e super-lattice) in small angle twisted double bilayer graphene (tDBLG) under the influence of external gate voltage and intrinsic spin-orbit coupling (SOC) for both AB-AB and AB-BA stacking configurations. Utilizing a low-energy continuum model, we investigate the band structure and perform a comprehensive topological characterization of the system by analysing the direct band gap closing as well as various Chern numbers. In the absence of SOC, the tDBLG exhibits characteristics of a valley Hall insulator. However, in the presence of SOC, we observe a transition to a quantum spin Hall insulator state and band topology emerges in the parameter spaces of non-topological regime without SOC. Furthermore, we conduct a comparative analysis between untwisted double bilayer graphene and tDBLG to assess the impact of twisting on the system's properties. Our findings reveal the construction of topological phase diagrams that showcase distinct phases arising from changes in the twist angle compared to the untwisted case. These phase diagrams provide valuable insights into the diverse topological phases achievable in tDBLG with SOC. Our findings contribute to the understanding of the interplay between small twist angle, SOC, and external electric field on the topological band properties of twisted multilayer graphene systems.

Berezinskii-Kosterlitz-Thouless to BCS-like superconducting transition crossover driven by weak magnetic fields in ultra-thin NbN films
Meenakshi Sharma, Sergio Caprara, Andrea Perali, Surinder P. Singh, Sandeep Singh, Nicola Pinto
arXiv:2403.11685v1 Announce Type: new Abstract: The Berezinskii-Kosterlitz-Thouless (BKT) transition in ultra-thin NbN films is investigated in the presence of weak perpendicular magnetic fields. A jump in the phase stiffness at the BKT transition is detected up to 5 G, while the BKT features are smeared between 5 G and 50 G, disappearing altogether at 100 G, where conventional current-voltage behaviour is observed. Our findings demonstrate that weak magnetic fields, insignificant in bulk systems, deeply affect our ultra-thin system, promoting a crossover from Halperin-Nelson fluctuations to a BCS-like state with Ginzburg-Landau fluctuations, as the field increases. This behavior is related to field-induced free vortices that screen the vortex-antivortex interaction and smear the BKT transition.

Layer dependent topological phases and transitions in TaRhTe$_4$: From monolayer and bilayer to bulk
Xiao Zhang, Ning Mao, Oleg Janson, Jeroen van den Brink, Rajyavardhan Ray
arXiv:2403.11688v1 Announce Type: new Abstract: The recently synthesized ternary quasi-2D material TaRhTe$_4$ is a bulk Weyl semimetal with an intrinsically layered structure, which poses the question how the topology of its electronic structure depends on layers separations. Experimentally these separations may be changed for instance by intercalation of the bulk, or by exfoliation to reach monolayer or few-layer structures. Here we show that in the monolayer limit a quantum spin Hall insulator (QSHI) state emerges, employing density functional calculations as well as a minimal four-orbital tight-binding model that we develop. Even for weak spin-orbit couplings the QSHI is present, which has an interesting edge state that features Rashba-split bands with quadratic band minima. Further we find that a weak topological insulator (WTI) manifests in the bilayer system due to sizable intralayer hopping, contrary to the common lore that only weak interlayer interactions between stacked QSHIs lead to WTIs. Stacked bilayers give rise to a phase diagram as function of the interlayer separation that comprises a Weyl semimetal, WTI and normal insulator phases. These insights on the evolution of topology with dimension can be transferred to the family of layered ternary transition metal tellurides.

Coarsening of chiral domains in itinerant electron magnets: A machine learning force field approach
Yunhao Fan, Sheng Zhang, Gia-Wei Chern
arXiv:2403.11705v1 Announce Type: new Abstract: Frustrated itinerant magnets often exhibit complex noncollinear or noncoplanar magnetic orders which support topological electronic structures. A canonical example is the anomalous quantum Hall state with a chiral spin order stabilized by electron-spin interactions on a triangular lattice. While a long-range magnetic order cannot survive thermal fluctuations in two dimensions, the chiral order which results from the breaking of a discrete Ising symmetry persists even at finite temperatures. We present a scalable machine learning (ML) framework to model the complex electron-mediated spin-spin interactions that stabilize the chiral magnetic domains in a triangular lattice. Large-scale dynamical simulations, enabled by the ML force-field models, are performed to investigate the coarsening of chiral domains after a thermal quench. While the chiral phase is described by a broken $Z_2$ Ising-type symmetry, we find that the characteristic size of chiral domains increases linearly with time, in stark contrast to the expected Allen-Cahn domain growth law for a non-conserved Ising order parameter field. The linear growth of the chiral domains is attributed to the orientational anisotropy of domain boundaries. Our work also demonstrates the promising potential of ML models for large-scale spin dynamics of itinerant magnets.

Tuning of the ultrafast demagnetization by ultrashort spin polarized currents in multi-sublattice ferrimagnets
Deeksha Gupta, Maryna Pankratova, Matthias Riepp, Manuel Pereiro, Biplab Sanyal, Soheil Ershadrad, Michel Hehn, Niko Pontius, Christian Sch\"u{\ss}ler-Langeheine, Nicolas Bergeard, Anders Bergman, Olle Eriksson, Christine Boeglin
arXiv:2403.11739v1 Announce Type: new Abstract: Femtosecond laser pulses can be used to induce ultrafast changes of the magnetization in magnetic materials. Several microscopic mechanisms have been proposed to explain the observations, including the transport of ultrashort spin-polarized hot-electrons (SPHE). Such ultrafast spin currents find growing interest because of the recent challenges in ultrafast spintronics however they are only poorly characterized. One of the key challenges is to characterize the spin-polarized ultrafast currents and the microscopic mechanisms behind SPHE induced manipulation of the magnetization, especially in the case of technologically relevant ferrimagnetic alloys. Here, we have used a combined approach using time- and element-resolved X-ray magnetic circular dichroism and theoretical calculations based on atomistic spin-dynamics simulations to address the ultrafast transfer of the angular momentum from spin-polarized currents into ferrimagnetic Fe74Gd26 films and the concomitant reduction of sub-lattice magnetization. Our study shows that using a Co/Pt multilayer as a polarizer in a spin-valve structure, the SPHE drives the demagnetization of the two sub-lattices of the Fe74Gd26 film. This behaviour is explained based on two physical mechanisms, i.e., spin transfer torque and thermal fluctuations induced by the SPHE. We provide a quantitative description of the heat transfer of the ultrashort SPHE pulse to the Fe74Gd26 films, as well as the degree of spin-polarization of the SPHE current density responsible for the observed magnetization dynamics. Our work finally characterizes the spin-polarization of the SPHEs revealing unexpected opposite spin polarization to the Co magnetization, explaining our experimental results.

Polarization multistates in composite ferroelectrics
Chuhan Tang, Zhiqiang Tian, Tao Ouyang, Anlian Pan, Mingxing Chen
arXiv:2403.11813v1 Announce Type: new Abstract: Going beyond the bistability paradigm of the charge polarizations in ferroelectrics is highly desired for ferroelectric memory devices toward ultra-high density information storage. Here, we propose to build multistates in composite ferroelectrics, which have both the intrinsic and sliding-induced polarizations. We illustrate the concept in H-stacking bilayers of 1T'' transition-metal dichalcogenides by first-principle calculations. We find that there is at least one order of magnitude difference in the energy barriers between these two types polarizations, which suggests that the external electric fields required to flipping them are significantly different. This difference allows for a novel flipping mechanism involving layer sliding and layer-by-layer flipping for the transforming of the polarization states. As a result, sextuple switchable states can be achieved for the 1T'' bilayers by properly controlling electrical field. Our study provides a new route to design polarization multistates for developing next-generation memory devices.

Discovery of self-assembled Ru/Si heterostructures with unique periodic nanostripe patterns boosting hydrogen evolution
Weizheng Cai, Xinyi He, Tian-Nan Ye, Xinmeng Hu, Chuanlong Liu, Masato Sasase, Masaaki Kitano, Toshio Kamiya, Hideo Hosono, Jiazhen Wu
arXiv:2403.11822v1 Announce Type: new Abstract: Two-dimensional (2D) heterostructuring is a versatile methodology for designing nanoarchitecture catalytic systems that allow for reconstruction and modulation of interfaces and electronic structures. However, catalysts with such structures are extremely scarce due to limited synthetic strategies. Here, we report a highly ordered 2D Ru/Si nano-heterostructures (RSHS) by acid etching of the LaRuSi electride. RSHS shows a superior electrocatalytic activity for hydrogen evolution with an overpotential of 14 mV at 10 mA/cm2 in alkaline media. Both experimental analysis and first-principles calculations demonstrate that the electronic states of Ru can be tuned by strong interactions of the interfacial Ru-Si, leading to an optimized hydrogen adsorption energy. Moreover, due to the synergistic effect of Ru and Si, the energy barrier of water dissociation is significantly reduced. The unique nanostripe structure with abundant interfaces in RSHS will provide a paradigm for construction of efficient catalysts with tunable electronic states and dual active sites.

Out-of-equilibrium scaling of the energy density along the critical relaxational flow after a quench of the temperature
Haralambos Panagopoulos, Ettore Vicari
arXiv:2403.11866v1 Announce Type: new Abstract: We study the out-of-equilibrium behavior of statistical systems along critical relaxational flows arising from instantaneous quenches of the temperature $T$ to the critical point $T_c$, starting from equilibrium conditions at time $t=0$. In the case of soft quenches, i.e. when the initial temperature $T$ is assumed sufficiently close to $T_c$ (to keep the system within the critical regime), the critical modes develop an out-of-equilibrium finite-size scaling (FSS) behavior in terms of the rescaled time variable $\Theta=t/L^z$, where $t$ is the time interval after quenching, $L$ is the size of the system, and $z$ is the dynamic exponent associated with the dynamics. However, the realization of this picture is less clear when considering the energy density, whose equilibrium scaling behavior (corresponding to the starting point of the relaxational flow) is generally dominated by a temperature-dependent regular background term or mixing with the identity operator. These issues are investigated by numerical analyses within the three-dimensional lattice $N$-vector models, for $N=3$ and $N=4$, which provide examples of critical behaviors with negative values of the specific-heat critical exponent $\alpha$, implying that also the critical behavior of the specific heat gets hidden by the background term. The results show that, after subtraction of its asymptotic critical value at $T_c$, the energy density develops an asymptotic out-of-equilibrium FSS in terms of $\Theta$ as well, whose scaling function appears singular in the small-$\Theta$ limit.

Topological edge modes and phase transition in the critical fermionic chain with long-range interaction
Wen-Hao Zhong, Wei-Lin Li, Yong-Chang Chen, Xue-Jia Yu
arXiv:2403.11880v1 Announce Type: new Abstract: The long-range interaction can fundamentally alter properties in gapped topological phases such as emergent massive edge modes. However, recent research has shifted attention to topological nontrivial critical points or phases, and it is natural to explore how long-range interaction influences them. In this work, we investigate the topological behavior and phase transition of extended Kitaev chains with long-range interactions, which can be derived from the critical Ising model via the Jordan-Wigner transformation in the short-range limit. Specifically, we analytically find the critical edge modes at the critical point remain stable against long-range interaction. More importantly, we observe these critical edge modes remain massless even when long-range interactions become substantially strong. As a byproduct, we numerically find that the critical behavior of the long-range model belongs to the free Majorana fermion universality class, which is entirely different from the long-range universality class in usual long-range spin models. Our work could shed new light on the interplay between long-range interactions (frustrated) and the gapless topological phases of matter.

A $C^\ast$-algebraic view on the interaction of real- and reciprocal space topology in skyrmion crystals
Pascal Prass, Fabian R. Lux, Emil Prodan, Duco van Straten, Yuriy Mokrousov
arXiv:2403.11912v1 Announce Type: new Abstract: Understanding the interaction of real- and reciprocal space topology in skyrmion crystals is an open problem. We approach it from the viewpoint of $C^\ast$-algebras and calculate all admissible Chern numbers of a strongly coupled tight-binding skyrmion system on a triangular lattice as a function of Fermi energy and texture parameters. Our analysis reveals the topological complexity of electronic states coupled to spin textures, and the failure of the adiabatic picture to account for it in terms of emergent electromagnetism. On the contrary, we explain the discontinuous jumps in the real-space winding number in terms of collective evolution in real-, reciprocal, and mixed space Chern numbers. Our work sets the stage for further research on topological dynamics in complex dynamic spin textures coupled to external fields.

Stacking-Configuration-Preserved Graphene Quantum Dots Electrochemically Obtained from CVD Graphene
Santiago D. Barrionuevo, Federico Fioravanti, Jorge M. Nu\~nez, David Mu\~neton Arboleda, Gabriela I. Lacconi, Martin G. Bellino, Myriam H. Aguirre, Francisco J. Iba\~nez
arXiv:2403.11922v1 Announce Type: new Abstract: The layer stacking morphology in nanocarbons is paramount for achieving new properties and outperforming applications. Here, we demonstrate that graphene quantum dots (GQDs) retain crystallinity and a stacking structure from CVD graphene grown on Ni foam. Our results reveal that GQD subdomains comprise a few-layer graphene structure in the AB -- AB and ABC -- ABC stacking configuration. HR-TEM images along with a multiple-approach characterization (XRD, XPS, UV-vis, AFM, and ATR-IR) exhibit 3.0 to 8.0 nm crystalline GQDs with 2-6 graphene layers thick indicating a disk-shape structure. The UV-vis profiles show changes in color of the dispersion (from colorless to red) during and after the electrochemistry, suggesting a systematic electrooxidation of graphene into smaller, highly crystalline, and more complex sp2/sp3 structures. Importantly, a control experiment performed under the same conditions but with a graphitic rod exhibited large, polydisperse, and multilayer carbon structures. This work demonstrates a relatively easy electrochemical synthesis to obtain GQDs which retain the pristine and, in turn, distinctive structure of graphene grown on Ni foam.

Uncovering the lowest thickness limit for room-temperature ferromagnetism of Cr$_{1.6}$Te$_{2}$
Sandeep Kumar Chaluvadi, Shyni Punathum Chalil, Anupam Jana, Deepak Dagur, Giovanni Vinai, Federico Motti, Jun Fujii, Moussa Mezhoud, Ulrike L\"uders, Vincent Polewczyk, Ivana Vobornik, Giorgio Rossi, Chiara Bigi, Younghun Hwang, Thomas Olsen, Pasquale Orgiani, Federico Mazzola
arXiv:2403.11977v1 Announce Type: new Abstract: Half-metallic ferromagnetic transition metal dichalcogenides have emerged as important building blocks for scalable magnonics and memory applications. Downscaling such systems to the ultra-thin limit is critical to integrate them into technology. Here, we achieved layer-by-layer control over the transition metal dichalcogenide Cr$_{1.6}$Te$_{2}$ by using pulsed laser deposition, and we uncovered the minimum critical thickness above which room temperature magnetic order is maintained. The electronic and magnetic structure is explored experimentally and theoretically and it is shown that the films exhibit strong in-plane magnetic anisotropy as a consequence of large spin-orbit effects. Our study establishes Cr$_{1.6}$Te$_{2}$ as a platform material, viable for ferromagnetic nanoscale devices and magnetic-memory architectures.

Exceptional points of any order in a generalized Hatano-Nelson model
Julius T. Gohsrich, Jacob Fauman, Flore K. Kunst
arXiv:2403.12018v1 Announce Type: new Abstract: Exceptional points (EPs) are truly non-Hermitian (NH) degeneracies where matrices become defective. The order of such an EP is given by the number of coalescing eigenvectors. On the one hand, most work focusses on studying $N$th-order EPs in $N\leq4$-dimensional NH Bloch Hamiltonians. On the other hand, some works have remarked on the existence of EPs of orders scaling with systems size in models exhibiting the NH skin effect. In this letter, we introduce a new type of EP and provide a recipe on how to realize EPs of arbitrary order not scaling with system size. We introduce a generalized version of the paradigmatic Hatano-Nelson model with longer-range hoppings. The EPs existing in this system show remarkable physical features: Their associated eigenstates are localized on a subset of sites and are exhibiting the NH skin effect. Furthermore, the EPs are robust against generic perturbations in the hopping strengths as well as against a specific form of on-site disorder.

Quantum memory at nonzero temperature in a thermodynamically trivial system
Yifan Hong, Jinkang Guo, Andrew Lucas
arXiv:2403.10599v1 Announce Type: cross Abstract: Passive error correction protects logical information forever (in the thermodynamic limit) by updating the system based only on local information and few-body interactions. A paradigmatic example is the classical two-dimensional Ising model: a Metropolis-style Gibbs sampler retains the sign of the initial magnetization (a logical bit) for thermodynamically long times in the low-temperature phase. Known models of passive quantum error correction similarly exhibit thermodynamic phase transitions to a low-temperature phase wherein logical qubits are protected by thermally stable topological order. Here, in contrast, we show that constant-rate classical and quantum low-density parity check codes have no $\textit{thermodynamic}$ phase transitions at nonzero temperature, but nonetheless exhibit $\textit{ergodicity-breaking}$ dynamical transitions: below a critical nonzero temperature, the mixing time of local Gibbs sampling diverges in the thermodynamic limit. We conjecture that the circuit complexity of preparing extensive-energy states may diverge without crossing any thermodynamic transition. Fault-tolerant passive decoders, inspired by Gibbs samplers, may be amenable to measurement-free quantum error correction and may present a desirable experimental alternative to conventional quantum error correction based on syndrome measurements and active feedback.

Good rates from bad coordinates: the exponential average time-dependent rate approach
Nicodemo Mazzaferro, Subarna Sasmal, Pilar Cossio, Glen M. Hocky
arXiv:2403.10668v1 Announce Type: cross Abstract: Our ability to calculate rates of biochemical processes using molecular dynamics simulations is severely limited by the fact that the time scales for reactions, or changes in conformational state, scale exponentially with the relevant free-energy barriers. In this work, we improve upon a recently proposed rate estimator that allows us to predict transition times with molecular dynamics simulations biased to rapidly explore one or several collective variables. This approach relies on the idea that not all bias goes into promoting transitions, and along with the rate, it estimates a concomitant scale factor for the bias termed the collective variable biasing efficiency $\gamma$. First, we demonstrate mathematically that our new formulation allows us to derive the commonly used Infrequent Metadynamics (iMetaD) estimator when using a perfect collective variable, $\gamma=1$. After testing it on a model potential, we then study the unfolding behavior of a previously well characterized coarse-grained protein, which is sufficiently complex that we can choose many different collective variables to bias, but which is sufficiently simple that we are able to compute the unbiased rate dire ctly. For this system, we demonstrate that our new Exponential Average Time-Dependent Rate (EATR) estimator converges to the true rate more rapidly as a function of bias deposition time than does the previous iMetaD approach, even for bias deposition times that are short. We also show that the $\gamma$ parameter can serve as a good metric for assessing the quality of the biasing coordinate. Finally, we demonstrate that the approach works when combining multiple less-than-optimal bias coordinates.

Coherent Acoustic Control of Defect Orbital States in the Strong-Driving Limit
B. A. McCullian, V. Sharma, H. Y. Chen, J. C. Crossman, E. J. Mueller, G. D. Fuchs
arXiv:2403.10989v1 Announce Type: cross Abstract: We use a bulk acoustic wave resonator to demonstrate coherent control of the excited orbital states in a diamond nitrogen-vacancy (NV) center at cryogenic temperature. Coherent quantum control is an essential tool for understanding and mitigating decoherence. Moreover, characterizing and controlling orbital states is a central challenge for quantum networking, where optical coherence is tied to orbital coherence. We study resonant multi-phonon orbital Rabi oscillations in both the frequency and time domain, extracting the strength of the orbital-phonon interactions and the coherence of the acoustically driven orbital states. We reach the strong-driving limit, where the physics is dominated by the coupling induced by the acoustic waves. We find agreement between our measurements, quantum master equation simulations, and a Landau-Zener transition model in the strong-driving limit. Using perturbation theory, we derive an expression for the orbital Rabi frequency versus acoustic drive strength that is non-perturbative in the drive strength and agrees well with our measurements for all acoustic powers. Motivated by continuous wave spin resonance-based decoherence protection schemes, we model the orbital decoherence and find good agreement between our model and our measured few-to-several nanoseconds orbital decoherence times. We discuss the outlook for orbital decoherence protection.

Kinetic inductance traveling wave amplifier designs for practical microwave readout applications
A. Giachero, M. Visser, J. Wheeler, L. Howe, J. Gao, J. Austermann, J. Hubmayr, A. Nucciotti3, J. Ullom
arXiv:2403.11354v1 Announce Type: cross Abstract: A Kinetic Inductance Traveling Wave amplifier (KIT) utilizes the nonlinear kinetic inductance of superconducting films, particularly Niobium Titanium Nitride (NbTiN), for parametric amplification. These amplifiers achieve remarkable performance in terms of gain, bandwidth, compression power, and frequently approach the quantum limit for noise. However, most KIT demonstrations have been isolated from practical device readout systems. Using a KIT as the first amplifier in the readout chain of an unoptimized microwave SQUID multiplexer coupled to a transition-edge sensor microcalorimeter we see an initial improvement in the flux noise. One challenge in KIT integration is the considerable microwave pump power required to drive the non-linearity. To address this, we have initiated efforts to reduce the pump power by using thinner NbTiN films and an inverted microstrip transmission line design. In this article, we present the new transmission line design, fabrication procedure, and initial device characterization -- including gain and added noise. These devices exhibit over 10 dB of gain with a 3 dB bandwidth of approximately 5.5-7.25 GHz, a maximum practical gain of 12 dB and typical gain ripple under 4 dB peak-to-peak. We observe an appreciable impedance mismatch in the NbTiN transmission line, which is likely the source of the majority of the gain ripple. Finally we perform an initial noise characterization and demonstrate system-added noise of three quanta or less over nearly the entire 3 dB bandwidth.

High-Fidelity Entangling Gates for Electron and Nuclear Spin Qubits in Diamond
Regina Finsterhoelzl, Wolf-R\"udiger Hannes, Guido Burkard
arXiv:2403.11553v1 Announce Type: cross Abstract: Motivated by the recent experimental progress in exploring the use of a nitrogen-vacancy (NV) center in diamond as a quantum computing platform, we propose schemes for fast and high-fidelity entangling gates on this platform. Using both analytical and numerical calculations, we demonstrate that synchronization effects between resonant and off-resonant transitions may be exploited such that spin-flip errors due to strong driving may be eliminated by adjusting the gate time or the driving field. This allows for fast, high fidelity entangling operations between the electron spin and one or several nuclear spins. We investigate a two-qubit system where the NV center is comprised of a $^{15}$N atom and a qubit-qutrit system for the case of a $^{14}$N atom. In both cases, we predict a complete suppression of off-resonant driving errors for two-qubit gates when addressing the NV electron spin conditioned on states of nuclear spins of the nitrogen atom of the defect. Additionally, we predict fidelities $>0.99$ for multi-qubit gates when including the surrounding $^{13}$C atoms in the diamond lattice in the conditioned logic.

Scattering Singularity in Topological Dielectric Photonic Crystals
Langlang Xiong, Xunya Jiang, Guangwei Hu
arXiv:2403.11613v1 Announce Type: cross Abstract: The exploration of topology in natural materials and metamaterials has garnered significant attention. Notably, the one-dimensional (1D) and two-dimensional (2D) Su-Schrieffer-Heeger (SSH) model, assessed through tight-binding approximations, has been extensively investigated in both quantum and classical systems, encompassing general and higher-order topology. Despite these advancements, a comprehensive examination of these models from the perspective of wave physics, particularly the scattering view, remains underexplored. In this study, we systematically unveil the origin of the 1D and 2D Zak phases stemming from the zero-scattering point, termed the scattering singularity in k-space. Employing an expanded plane wave expansion, we accurately compute the reflective spectrum of an infinite 2D photonic crystal (2D-PhC). Analyzing the reflective spectrum reveals the presence of a zero-scattering line in the 2D-PhC, considered the topological origin of the non-trivial Zak phase. Two distinct models, representing omnidirectional non-trivial cases and directional non-trivial cases, are employed to substantiate these findings. Our work introduces a novel perspective for characterizing the nature of non-trivial topological phases. The identification of the zero-scattering line not only enhances our understanding of the underlying physics but also provides valuable insights for the design of innovative devices.

Electrolubrication in flowing liquid mixtures
Yoav Tsori
arXiv:2403.11846v1 Announce Type: cross Abstract: We describe the ``electrolubrication'' occurring in liquid mixtures confined between two charged surfaces. For a mixture of two liquids, the effective viscosity decreases markedly in the presence of a field. The origin of this reduction is field-induced phase separation, leading to the formation of two low-viscosity lubrication layers at the surfaces. These layers facilitate larger strain at a given stress. The effect is strong if the viscosities of the two liquids are sufficiently different, the volume fraction of the less viscous liquid is small, the gap between the surfaces is small, and the applied potential is large. The phase separation relies on the existence of dissociated ions in the solution. The effective viscosity is reduced by a factor $\alpha$; its maximum value is the ratio between the viscosities of the two liquids. In most liquids, $\alpha \sim1 $ -- $10$, and in mixtures of water and glycerol $\alpha \sim 80$ -- $100$ under relatively small potentials.

Accelerating Scientific Discovery with Generative Knowledge Extraction, Graph-Based Representation, and Multimodal Intelligent Graph Reasoning
Markus J. Buehler
arXiv:2403.11996v1 Announce Type: cross Abstract: Using generative Artificial Intelligence (AI), we transformed a set of 1,000 scientific papers in the area of biological materials into detailed ontological knowledge graphs, revealing their inherently scale-free nature. Using graph traversal path detection between dissimilar concepts based on combinatorial ranking of node similarity and betweenness centrality, we reveal deep insights into unprecedented interdisciplinary relationships that can be used to answer queries, identify gaps in knowledge, and propose never-before-seen material designs and their behaviors. One comparison revealed detailed structural parallels between biological materials and Beethoven's 9th Symphony, highlighting shared patterns of complexity through isomorphic mapping. The algorithm further created an innovative hierarchical mycelium-based composite that incorporates joint synthesis of graph sampling with principles extracted from Kandinsky's Composition VII painting, where the resulting composite reflects a balance of chaos and order, with features like adjustable porosity, mechanical strength, and complex patterned chemical functionalization. We uncover other isomorphisms across physical, biological, and artistic spheres, revealing a nuanced ontology of immanence and material flux that resonates with postmodern philosophy, and positions these interconnections within a heterarchical framework. Our findings reveal the dynamic, context-dependent interplay of entities beyond traditional hierarchical paradigms, emphasizing the significant role of individual components and their fluctuative relationships within the system. Our predictions achieve a far higher degree of novelty, technical detail and explorative capacity than conventional generative AI methods. The approach establishes a widely useful framework for innovation by revealing hidden connections that facilitate discovery.

Atomic and electronic structure of defects in hBN: enhancing single-defect functionalities
Z. Qiu, K. Vaklinova, P. Huang, M. Grzeszczyk, H. Yang, K. Watanabe, T. Taniguchi, K. S. Novoselov, J. Lu, M. Koperski
arXiv:2110.07842v2 Announce Type: replace Abstract: Defect centers in insulators play a critical role in creating important functionalities in materials: prototype qubits, single-photon sources, magnetic field probes, and pressure sensors. These functionalities are highly dependent on their mid-gap electronic structure and orbital/spin wave-function contributions. However, in most cases, these fundamental properties remain unknown or speculative due to the defects being deeply embedded beneath the surface of highly resistive host crystals, thus impeding access through surface probes. Here, we directly inspected the atomic and electronic structures of defects in thin carbon-doped hexagonal boron nitride (hBN:C) using scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS). Such investigation adds direct information about the electronic mid-gap states to the well-established photoluminescence response (including single photon emission) of intentionally created carbon defects in the most commonly investigated van der Waals insulator. Our joint atomic-scale experimental and theoretical investigations reveal two main categories of defects: 1) single-site defects manifesting as donor-like states with atomically resolved structures observable via STM, and 2) multi-site defect complexes exhibiting a ladder of empty and occupied mid-gap states characterized by distinct spatial geometries. Combining direct probing of mid-gap states through tunneling spectroscopy with the inspection of the optical response of insulators hosting specific defect structures holds promise for creating and enhancing functionalities realized with individual defects in the quantum limit. These findings underscore not only the versatility of hBN:C as a platform for quantum defect engineering but also its potential to drive advancements in atomic-scale optoelectronics.

Electrically Controlled Anomalous Hall Effect and Orbital Magnetization in Topological Magnet MnBi2Te4
Ruobing Mei, Yi-Fan Zhao, Chong Wang, Yafei Ren, Di Xiao, Cui-Zu Chang, Chao-Xing Liu
arXiv:2303.06204v4 Announce Type: replace Abstract: In this work, we propose an intrinsic mechanism to understand the even-odd effect, namely the opposite signs of the anomalous Hall resistance and the different shapes of hysteresis loops for even and odd septuple layers (SLs), of MBE-grown MnBi2Te4 thin films with electron doping. In particular, we show that the non-zero hysteresis loops in the anomalous Hall and magnetic circular dichroism measurements for even-SLs MnBi2Te4 films are originated from two different anti-ferromagnetic (AFM) states with opposite magnetoelectric coefficients that give rise to different energies of zeroth Landau levels of the surface states in this model. The complex form of the anomalous Hall hysteresis loop in even-SLs MnBi2Te4 films can be understood from two magnetic transitions, a transition from one AFM state to the other AFM state followed by a second transition to the ferromagnetic state. Our model also provides a microscopic understanding of the electrical switching between two AFM states via the axion electrodynamics in even-SL MnBi2Te4 films. We further study orbital magnetization and magnetoelectric coefficient in MnBi2Te4 films, and find an even-odd oscillation behavior of the magnetoelectric coefficient.

Parsing skin effect in a non-Hermitian spinless BHZ-like model
Dipendu Halder, Saurabh Basu
arXiv:2304.12723v2 Announce Type: replace Abstract: This work comprehensively investigates the non-Hermitian skin effect (NHSE) in a spinless Bernevig-Hughes-Zhang (BHZ)-like model in one dimension. It is generally believed that a system with non-reciprocal hopping amplitudes demonstrates NHSE. However, we show that there are exceptions, and more in-depth analyses are required to decode the presence of NHSE or its variants in a system. The fascinating aspects of our findings, depending on the inclusion of non-reciprocity in the inter-orbital hopping terms, concede the existence of conventional or bi-directional NHSE and even a surprising absence of NHSE. The topological properties and the (bi-orthogonal) bulk-boundary correspondence, enumerated via computation of the (complex) Berry phase, the winding number, and spatial localization of the edge modes, highlight the topological phase transitions occurring therein. Further, to facilitate a structured discussion of the non-Hermitian model, we split the results into PT symmetric and non-PT symmetric cases with a view to comparing the two.

Unconventional phonon spectra and obstructed edge phonon modes
Ruihan Zhang, Haohao Sheng, Junze Deng, Zhong Fang, Zhilong Yang, Zhijun Wang
arXiv:2305.09453v2 Announce Type: replace Abstract: Based on the elementary band representations (EBR), some topologically trivial materials are classified as unconventional ones (obstructed atomic limit), where the EBR decomposition of electronic states is not consistent with the atomic valence-electron band representations. In the work, we identify that the unconventional nature can also exist in phonon spectra, where the EBR decomposition of the phonon modes is not consistent with atomic vibration band representations (ABR). The unconventionality has two types: type I is on an empty site; type II is on an atom site with non-atomic vibration orbitals. Our detailed calculations show that black phosphorus (BP) and 1H-MoSe2 have unconventional both phonon spectra and electronic band structures. The BP has the type-I unconventional phonon spectrum, while 1H-MoSe2 has the type-II one. The obstructed phonon modes are obtained for two types of unconventional phonon spectra.

Superconductivity in unconventional metals
Zhilong Yang, Haohao Sheng, Zhaopeng Guo, Ruihan Zhang, Quansheng Wu, Hongming Weng, Zhong Fang, Zhijun Wang
arXiv:2306.08347v2 Announce Type: replace Abstract: Based on first-principles calculations, we demonstrate that 1H/2H-phase transition metal dichalcogenides MX2 (M=Nb,Ta; X=S,Se,Te) are unconventional metals, which have an empty-site band of $A_1'@1e$ elementary band representation at the Fermi level. The computed phonon dispersions indicate the stability of the system at high temperatures, while the presence of the soft phonon mode suggests a phase transition to the charge density wave state at low temperatures. Based on the Bardeen-Cooper-Schrieffer theory and computed electron-phonon coupling, our calculations show that the superconductivity (SC) in NbSe2 is mainly attributed to the soft phonon mode due to the half filling of the empty-site band. Accordingly, the SC has been predicted in unconventional metals TaNS monolayer and 2H-TaN2 bulk with computed $T_C=$ 10 K and 26 K respectively. These results demonstrate that the unconventional metals with partial filling of the empty-site band offer an attractive platform to search for superconductors.

Test for BCS-BEC Crossover in the Cuprate Superconductors
Qijin Chen, Zhiqiang Wang, Rufus Boyack, K. Levin
arXiv:2307.08611v3 Announce Type: replace Abstract: In this paper we address the question of whether high-temperature superconductors have anything in common with BCS-BEC crossover theory. Towards this goal, we present a proposal and related predictions which provide a concrete test for the applicability of this theoretical framework. These predictions characterize the behavior of the Ginzburg-Landau coherence length, $\xi_0^{\text{coh}}$, near the transition temperature $T_{\text{c}}$, and across the entire superconducting $T_{\text{c}}$ dome in the phase diagram. That we are lacking a systematic characterization of $\xi_0^{\text{coh}}$ in the entire class of cuprate superconductors is perhaps surprising, as it is one of the most fundamental properties of any superconductor. This paper is written to motivate further experiments and, thus, address this shortcoming. Here we show how measurements of $\xi_0^{\text{coh}}$ contain direct indications for whether or not the cuprates are associated with BCS-BEC crossover and, if so, where within the crossover spectrum a particular superconductor lies.

Observation of giant nonreciprocal charge transport from quantum Hall states in a topological insulator
Chunfeng Li, Rui Wang, Shuai Zhang, Yuyuan Qin, Zhe Ying, Boyuan Wei, Zheng Dai, Fengyi Guo, Wei Chen, Rong Zhang, Baigeng Wang, Xuefeng Wang, Fengqi Song
arXiv:2307.08917v3 Announce Type: replace Abstract: Symmetry breaking in quantum materials is of great importance and can lead to nonreciprocal charge transport. Topological insulators provide a unique platform to study nonreciprocal charge transport due to their surface states, especially quantum Hall states under external magnetic field. Here, we report the observation of nonreciprocal charge transport mediated by quantum Hall states in devices composed of the intrinsic topological insulator Sn-Bi1.1Sb0.9Te2S, which is attributed to asymmetric scattering between quantum Hall states and Dirac surface states. A giant nonreciprocal coefficient of up to 2.26*10^5 A^-1 is found. Our work not only reveals the properties of nonreciprocal charge transport of quantum Hall states in topological insulators, but also paves the way for future electronic devices.

Disorder Operator and R\'enyi Entanglement Entropy of Symmetric Mass Generation
Zi Hong Liu, Yuan Da Liao, Gaopei Pan, Menghan Song, Jiarui Zhao, Weilun Jiang, Chao-Ming Jian, Yi-Zhuang You, Fakher F. Assaad, Zi Yang Meng, Cenke Xu
arXiv:2308.07380v5 Announce Type: replace Abstract: In recent years a consensus has gradually been reached that the previously proposed deconfined quantum critical point (DQCP) for spin-1/2 systems, an archetypal example of quantum phase transition beyond the classic Landau's paradigm, actually does not correspond to a true unitary conformal field theory (CFT). In this work we carefully investigate another type of quantum phase transition supposedly beyond the similar classic paradigm, the so called ``symmetric mass generation" (SMG) transition proposed in recent years. We employ the sharp diagnosis including the scaling of disorder operator and R\'enyi entanglement entropy in large-scale lattice model quantum Monte Carlo simulations. Our results strongly suggest that the SMG transition is indeed an unconventional quantum phase transition and it should correspond to a true $(2+1)d$ unitary CFT.

Non-centrosymmetric, transverse structural modulation in SrAl4, and elucidation of its origin in the BaAl4 family of compounds
Sitaram Ramakrishnan, Surya Rohith Kotla, Hanqi Pi, Bishal Baran Maity, Jia Chen, Jin-Ke Bao, Zhaopeng Guo, Masaki Kado, Harshit Agarwal, Claudio Eisele, Minoru Nohara, Leila Noohinejad, Hongming Weng, Srinivasan Ramakrishnan, Arumugam Thamizhavel, Sander van Smaalen
arXiv:2309.08959v3 Announce Type: replace Abstract: At ambient conditions SrAl4 adopts the BaAl4 structure type with space group I4/mmm. It undergoes a charge-density-wave (CDW) transition at TCDW = 243 K, followed by a structural transition at TS = 87 K. Temperature-dependent single-crystal X-ray diffraction (SXRD) leads to the observation of incommensurate superlattice reflections at q = \sigma c* with \sigma = 0.1116 at 200 K. The CDW has orthorhombic symmetry with the acentric superspace group F222(00sigma)00s, where F222 is a subgroup of Fmmm as well as of I4/mmm. Atomic displacements mainly represent a transverse wave, with displacements that are 90 deg out of phase between the two diagonal directions of the I-centered unit cell, resulting in a helical wave. Small longitudinal displacements are provided by the second harmonic modulation. The orthorhombic phase realized in SrAl4 is similar to that found in EuAl4. Electronic structure calculations and phonon calculations by density functional theory (DFT) have failed to reveal the mechanism of CDW formation. However, DFT reveals that Al atoms dominate the density of states near the Fermi level, thus, corroborating the SXRD measurements. SrAl4 remains incommensurately modulated at the structural transition, where the symmetry lowers from orthorhombic to b-unique monoclinic. We have identified a simple criterion, that correlates the presence of a phase transition with the interatomic distances. Only those compounds XAl4-xGax(X = Ba, Eu, Sr, Ca; 0 < x <4) undergo phase transitions, for which the ratio c/a falls within the narrow range 2.51 < c/a < 2.54.

Phase transitions in the anisotropic XY ferromagnet with quenched nonmagnetic impurity
Olivia Mallick, Muktish Acharyya
arXiv:2309.09659v3 Announce Type: replace Abstract: The three dimensional anisotropic XY ferromagnet has been studied by Monte Carlo simulation. The ferro-para phase transition has been observed to take place at a lower temperature for impure anisotropic XY ferromagnet. The pseudocritical temperature ($T_c^*$) has been found to decrease as the system gets more and more impure (impurity concentration $p$ increases). In the case of bilinear exchange type of anisotropy ($\lambda$), the pseudocritical temperature ($T_c^*$) increases linearly with $\lambda$ for any given concentration of nonmagnetic impurity ($p$). The slope of this linear function has been found to depend on the impurity concentration ($p$). The slope decreases linearly with the impurity concentration ($p$). In the case of the single site anisotropy ($D$), the pseudocritical temperature ($T_c^*$) has been found to decrease linearly with $p$ for fixed $D$. The critical temperature (for a fixed set of parameter values) has been estimated from the temperature variation of fourth order Binder cumulants ($U_L$) for different system sizes ($L$). The critical magnetisation ($M(T_c)$) and the maximum value of the susceptibility ($\chi_p$) are calculated for different system sizes ($L$). The critical exponents for the assumed scaling laws, $M(T_c) \sim L^{-{{\beta} \over {\nu}}}$ and $\chi_p \sim L^{{{\gamma} \over {\nu}}}$, are estimated through the finite size analysis. We have estimated, ${{\beta} \over {\nu}}$, equals to $0.48\pm0.05$ and $0.37\pm0.04$ for bilinear exchange and single site anisotropy respectively. We have also estimated, ${{\gamma} \over {\nu}}$ equals to $1.78\pm0.05$ and $1.81\pm0.05$ for bilinear exchange and single site anisotropy respectively.

Superconductivity emerging from density-wave-like order in a correlated kagome metal
Yi Liu, Zi-Yi Liu, Jin-Ke Bao, Peng-Tao Yang, Liang-Wen Ji, Si-Qi Wu, Qin-Xin Shen, Jun Luo, Jie Yang, Ji-Yong Liu, Chen-Chao Xu, Wu-Zhang Yang, Wan-Li Chai, Jia-Yi Lu, Chang-Chao Liu, Bo-Sen Wang, Hao Jiang, Qian Tao, Zhi Ren, Xiao-Feng Xu, Chao Cao, Zhu-An Xu, Rui Zhou, Jin-Guang Cheng, Guang-Han Cao
arXiv:2309.13514v2 Announce Type: replace Abstract: Unconventional superconductivity (USC) in a highly correlated kagome system has been theoretically proposed for years, yet the experimental realization is hard to achieve. The recently discovered vanadium-based kagome materials, which exhibit both superconductivity and charge density wave (CDW) orders, are nonmagnetic and weakly correlated, thus unlikely host USC as theories proposed. Here we report the discovery of a chromium-based kagome metal, CsCr$_3$Sb$_5$, which is contrastingly characterised by strong electron correlations, frustrated magnetism, and characteristic flat bands close to the Fermi level. Under ambient pressure, it undergoes a concurrent structural and magnetic phase transition at 55 K, accompanying with a stripe-like $4a_0$ structural modulation. At high pressure, the phase transition evolves into two transitions, probably associated with CDW and antiferromagnetic spin-density-wave orderings, respectively. These density-wave (DW)-like orders are gradually suppressed with pressure and, remarkably, a superconducting dome emerges at 3.65-8.0 GPa. The maximum of the superconducting transition temperature, $T_\mathrm{c}^{\mathrm{max}}=$ 6.4 K, appears when the DW-like orders are completely suppressed at 4.2 GPa, and the normal state exhibits a non-Fermi-liquid behaviour, reminiscent of USC and quantum criticality in iron-based superconductors. Our work offers an unprecedented platform for investigating possible USC in a correlated kagome system.

Spin-orbit excitons in a correlated metal: Raman scattering study of Sr2RhO4
Lichen Wang, Huimei Liu, Valentin Zimmermann, Arvind Kumar Yogi, Masahiko Isobe, Matteo Minola, Matthias Hepting, Giniyat Khaliullin, Bernhard Keimer
arXiv:2309.15299v2 Announce Type: replace Abstract: Using Raman spectroscopy to study the correlated 4$d$-electron metal Sr$_2$RhO$_4$, we observe pronounced excitations at 220 meV and 240 meV with $A_\mathrm{1g}$ and $B_\mathrm{1g}$ symmetries, respectively. We identify them as transitions between the spin-orbit multiplets of the Rh ions, in close analogy to the spin-orbit excitons in the Mott insulators Sr$_2$IrO$_4$ and $\alpha$-RuCl$_3$. This observation provides direct evidence for the unquenched spin-orbit coupling in Sr$_2$RhO$_4$. A quantitative analysis of the data reveals that the tetragonal crystal field $\Delta$ in Sr$_2$RhO$_4$ has a sign opposite to that in insulating Sr$_2$IrO$_4$, which enhances the planar $xy$ orbital character of the effective $J=1/2$ wave function. This supports a metallic ground state, and suggests that $c$-axis compression of Sr$_2$RhO$_4$ may transform it into a quasi-two-dimensional antiferromagnetic insulator.

Nonequilibrium protection and spatial localization of noise-induced fluctuations: quasi-one-dimensional driven lattice gas with partially penetrable obstacle
S. P. Lukyanets, O. V. Kliushnichenko
arXiv:2311.11658v3 Announce Type: replace Abstract: We consider a nonequilibrium transition that leads to the formation of nonlinear steady-state structures due to the gas flow scattering on a partially penetrable obstacle. The resulting nonequilibrium steady state (NESS) corresponds to a two-domain gas structure attained at certain critical parameters. We use a simple mean-field model of the driven lattice gas with ring topology to demonstrate that this transition is accompanied by the emergence of local invariants related to a complex composed of the obstacle and its nearest gas surrounding, which we refer to as obstacle edges. These invariants are independent of the main system parameters and behave as local first integrals, at least qualitatively. As a result, the complex becomes insensitive to the noise of external driving field within the overcritical domain. The emerged invariants describe the conservation of the number of particles inside the obstacle and strong temporal synchronization or correlation of gas states at obstacle edges. Such synchronization guarantees the equality to zero of the total edge current at any time. The robustness against external drive fluctuations is shown to be accompanied by strong spatial localization of induced gas fluctuations near the domain wall separating the depleted and dense gas phases. Such a behavior can be associated with nonequilibrium protection effect and synchronization of edges. The transition rates between different NESSs are shown to be different. The relaxation rates from one NESS to another take complex and real values in the sub- and overcritical regimes, respectively. The mechanism of these transitions is governed by the generation of shock waves at the back side of the obstacle. In the subcritical regime, these solitary waves are generated sequentially many times, while only a single excitation is sufficient to rearrange the system state in the overcritical regime.

Co-orchestration of Multiple Instruments to Uncover Structure-Property Relationships in Combinatorial Libraries
Boris N. Slautin, Utkarsh Pratiush, Ilia N. Ivanov, Yongtao Liu, Rohit Pant, Xiaohang Zhang, Ichiro Takeuchi, Maxim A. Ziatdinov, Sergei V. Kalinin
arXiv:2402.02198v2 Announce Type: replace Abstract: The rapid growth of automated and autonomous instrumentations brings forth an opportunity for the co-orchestration of multimodal tools, equipped with multiple sequential detection methods, or several characterization tools to explore identical samples. This can be exemplified by the combinatorial libraries that can be explored in multiple locations by multiple tools simultaneously, or downstream characterization in automated synthesis systems. In the co-orchestration approaches, information gained in one modality should accelerate the discovery of other modalities. Correspondingly, the orchestrating agent should select the measurement modality based on the anticipated knowledge gain and measurement cost. Here, we propose and implement a co-orchestration approach for conducting measurements with complex observables such as spectra or images. The method relies on combining dimensionality reduction by variational autoencoders with representation learning for control over the latent space structure, and integrated into iterative workflow via multi-task Gaussian Processes (GP). This approach further allows for the native incorporation of the system's physics via a probabilistic model as a mean function of the GP. We illustrated this method for different modalities of piezoresponse force microscopy and micro-Raman on combinatorial $Sm-BiFeO_3$ library. However, the proposed framework is general and can be extended to multiple measurement modalities and arbitrary dimensionality of measured signals. The analysis code that supports the funding is publicly available at https://github.com/Slautin/2024_Co-orchestration.

Entanglement Microscopy: Tomography and Entanglement Measures via Quantum Monte Carlo
Ting-Tung Wang, Menghan Song, Liuke Lyu, William Witczak-Krempa, Zi Yang Meng
arXiv:2402.14916v2 Announce Type: replace Abstract: We develop a protocol, dubbed entanglement microscopy, to obtain the full reduced density matrix associated with subregions in quantum Monte Carlo simulations for bosonic and fermionic manybody systems. Our microscopy allows to perform quantum state tomography, and thus gives access to true entanglement measures, such as the logarithmic negativity (LN). We exemplify our method by studying the phase diagram near quantum critical points (QCP) in 2 spatial dimensions: the transverse field Ising model and a Gross-Neveu-Yukawa transition of Dirac fermions. Our main results are: i) the Ising QCP exhibits short-range entanglement with a finite sudden death of the LN both in space and temperature; ii) the Gross-Neveu QCP has a power-law decaying fermionic LN consistent with conformal field theory (CFT) exponents; iii) going beyond bipartite entanglement, we find no detectable 3-party entanglement in a large parameter window near the Ising QCP in 2d, in contrast to 1d. We also analytically obtain the large-temperature power law scaling of the fermionic LN for general interacting systems. Our approach allows one to perform quantum state tomography locally in a way that is analogous to atomic-scale imaging with a scanning tunneling microscope. Controlled entanglement microscopy opens a new window into quantum matter, with countless systems waiting to be explored.

Topologically protected emergent Fermi surface in an Abrikosov vortex lattice
Songyang Pu, Jay D. Sau, Rui-Xing Zhang
arXiv:2402.18627v2 Announce Type: replace Abstract: We show that a three-dimensional (3D) fully gapped type-II superconductor can feature emergent in-gap Fermi surfaces of Caroli-de Gennes Matricon (CdGM) quasiparticles in the presence of an Abrikosov vortex lattice. In particular, these CdGM Fermi surfaces manifest in the emergent 3D band structure enabled by the intervortex tunneling physics, and their stability is guaranteed by a $\mathbb{Z}_2$ topological index. By developing an effective analytical theory, we find that each vortex line carrying a 1D nodal dispersion is a sufficient condition for the vortex lattice to form CdGM Fermi surfaces. Following this prediction, in-gap CdGM Fermi surfaces are numerically confirmed in a microscopic vortex-lattice simulation of a superconducting Dirac semimetal with an $s$-wave spin-singlet pairing, which is directly applicable to a large class of type-II superconductors such as LiFeAs. Remarkably, the CdGM Fermi surfaces persist even when the normal state is deformed to a doped insulator of trivial band topology. Our work establishes the vortex lattice as a new experimentally feasible control knob for emergent topological phenomena in conventional superconductors.

Blume-Capel model analysis with microcanonical population annealing method
Vyacheslav Mozolenko, Lev Shchur
arXiv:2402.18985v2 Announce Type: replace Abstract: We present a modification of the Rose-Machta algorithm (Phys. Rev. E 100 (2019) 063304) and estimate the density of states for a two-dimensional Blume-Capel model, simulating $10^5$ replicas in parallel for each set of parameters. We perform a finite-size analysis of the specific heat and Binder cumulant, determine the critical temperature along the critical line, and evaluate the critical exponents. The results obtained are in good agreement with those obtained previously using various methods -- Markov Chain Monte Carlo simulation, Wang-Landau simulation, transfer matrix, and series expansion. The simulation results clearly illustrate the typical behavior of specific heat along the critical lines and through the tricritical point.

Suppressed weak anti-localization in topological insulator - antiferromagnetic insulator (BiSb)$_2$Te$_3$ - MnF$_2$ thin film bilayers
Ryan Van Haren, David Lederman
arXiv:2403.03116v2 Announce Type: replace Abstract: Thin films of the topological insulator (BiSb)$_2$Te$_3$ oriented along the [0001] direction were grown via molecular beam epitaxy on substrates of Al$_2$O$_3$ (0001) and MgF$_2$ (110) single crystals, as well as on an epitaxial thin film of the antiferromagnetic insulator MnF$_2$ (110). Magnetoconductivity measurements of these samples showed close proximity of the Fermi level to the Dirac point and weak antilocalization at low temperature that was partially suppressed in the sample grown on the MnF$_2$ layer. The magnetoconductivity data were fit to a model that describes the quantum corrections to the conductivity for the Dirac surface state of a 3-dimensional topological insulator, from which values of the Fermi velocity and the phase coherence length of the surface state charge carriers were derived. The magnetoconductivity of the (BiSb)$_2$Te$_3$ - MnF$_2$ bilayer samples were fit to a model describing the crossover from weak antilocalization to weak localization due to magnetic doping. The results are consistent with the opening of an energy gap at the Dirac point in the (BiSb)$_2$Te$_3$ due to magnetic proximity interactions of the topological surface states with the antiferromagnetic MnF$_2$ insulator.

The Uhlmann Phase Winding in Bose-Einstein Condensates at Finite Temperature
Chang-Yan Wang, Yan He
arXiv:2403.05127v2 Announce Type: replace Abstract: We investigate the Uhlmann phase, a generalization of the celebrated Berry phase, for Bose-Einstein condensates (BECs) at finite temperature. The Uhlmann phase characterizes topological properties of mixed states, in contrast to the Berry phase which is defined for pure states at zero temperature. Using the $SU(1,1)$ symmetry of the Bogoliubov Hamiltonian, we derive a general formula for the Uhlmann phase of BECs. Numerical calculations reveal that the Uhlmann phase can differ from the Berry phase in the zero-temperature limit, contrary to previous studies. As the temperature increases, the Uhlmann phase exhibits a winding behavior, and we relate the total winding degree to the Berry phase. This winding indicates that the Uhlmann phase takes values on a Riemann surface. Furthermore, we propose an experimental scheme to measure the Uhlmann phase of BECs by purifying the density matrix using an atomic interferometer.

Topological Optical Spin Injection Beyond Regular Weyl semimetals
Suvendu Ghosh, Chuanchang Zeng, A. Taraphder, Jian-Xin Zhu, Snehasish Nandy
arXiv:2403.09235v2 Announce Type: replace Abstract: Photoinduced effects are now reckoned to be important tools to reveal a rich gamut of entrancing physics in topological materials, which are normally inaccessible via conventional probes. Here we investigate one of these intriguing effects, namely, {\it optical spin injection} (OSI) beyond the regular Weyl semimetal (WSM), specifically in multi- and higher-order WSMs. Remarkably, we demonstrate that OSI in multi-WSMs can emerge as a frequency-independent quantized response engendered by band linearity and topological charge associated with the node. Interestingly, the frequency independence can be destroyed by going beyond the first-order topological phase where we explicitly show the OSI response is accompanied by peaks for the first-order Weyl nodes while dips for the second-order Weyl nodes. In addition, we elucidate the behavior of OSI in type-II Weyl phases. The predicted signatures of OSI beyond the regular WSM, i.e., multi- and higher-order WSM, could be experimentally exploited, leading us to effectively access as well as distinguish different-order nontrivial Weyl topology.

Classical shadows based on locally-entangled measurements
Matteo Ippoliti
arXiv:2305.10723v3 Announce Type: replace-cross Abstract: We study classical shadows protocols based on randomized measurements in $n$-qubit entangled bases, generalizing the random Pauli measurement protocol ($n = 1$). We show that entangled measurements ($n\geq 2$) enable nontrivial and potentially advantageous trade-offs in the sample complexity of learning Pauli expectation values. This is sharply illustrated by shadows based on two-qubit Bell measurements: the scaling of sample complexity with Pauli weight $k$ improves quadratically (from $\sim 3^k$ down to $\sim 3^{k/2}$) for many operators, while others become impossible to learn. Tuning the amount of entanglement in the measurement bases defines a family of protocols that interpolate between Pauli and Bell shadows, retaining some of the benefits of both. For large $n$, we show that randomized measurements in $n$-qubit GHZ bases further improve the best scaling to $\sim (3/2)^k$, albeit on an increasingly restricted set of operators. Despite their simplicity and lower hardware requirements, these protocols can match or outperform recently-introduced "shallow shadows" in some practically-relevant Pauli estimation tasks.

Anomaly Enforced Gaplessness for Background Flux Anomalies and Symmetry Fractionalization
T. Daniel Brennan, Aiden Sheckler
arXiv:2311.00093v2 Announce Type: replace-cross Abstract: Anomalous symmetries are known to strongly constrain the possible IR behavior along any renormalization group (RG) flow. Recently, the extension of the notion of symmetry in QFT has provided new types of anomalies with a corresponding new class of constraints on RG flows. In this paper, we derive the constraints imposed on RG flows from anomalies that can only be activated in the presence of specific background fluxes even though they do not necessarily correspond to a symmetry. We show that such anomalies can only be matched by gapped theories that exhibit either spontaneous symmetry breaking or symmetry fractionalization. In addition, we exhibit previously unstudied examples of these flux background anomalies that arise in $4d$ QCD and $4d$ SUSY QCD.

Alternant Hydrocarbon Diradicals as Optically Addressable Molecular Qubits
Yong Rui Poh, Dmitry Morozov, Nathanael P. Kazmierczak, Ryan G. Hadt, Gerrit Groenhof, Joel Yuen-Zhou
arXiv:2403.09102v2 Announce Type: replace-cross Abstract: High-spin molecules allow for bottom-up qubit design and are promising platforms for magnetic sensing and quantum information science. Optical addressability of molecular electron spins has also been proposed in first-row transition metal complexes via optically-detected magnetic resonance (ODMR) mechanisms analogous to the diamond-NV colour centre. However, significantly less progress has been made on the front of metal-free molecules, which can deliver lower costs and milder environmental impacts. At present, most luminescent open-shell organic molecules are $\pi$-diradicals, but such systems often suffer from poor ground-state open-shell characters necessary to realise a stable ground-state molecular qubit. In this work, we use alternancy symmetry to selectively minimise radical-radical interactions in the ground state, generating $\pi$-systems with high diradical characters. We call them m-dimers, referencing the need to covalently link two benzylic radicals at their meta carbon atoms for the desired symmetry. Through a detailed electronic structure analysis, we find that the excited states of alternant hydrocarbon m-diradicals contain important symmetries that can be used to construct ODMR mechanisms leading to ground-state spin polarisation. The molecular parameters are set in the context of a tris(2,4,6-trichlorophenyl)methyl (TTM) radical dimer covalently tethered at the meta position, demonstrating the feasibility of alternant m-diradicals as molecular colour centres.

Found 16 papers in prb
Date of feed: Tue, 19 Mar 2024 04:17:07 GMT

Search terms: (topolog[a-z]+)|(graphit[a-z]+)|(rhombohedr[a-z]+)|(graphe[a-z]+)|(chalcog[a-z]+)|(landau)|(weyl)|(dirac)|(STM)|(scan[a-z]+ tunne[a-z]+ micr[a-z]+)|(scan[a-z]+ tunne[a-z]+ spectr[a-z]+)|(scan[a-z]+ prob[a-z]+ micr[a-z]+)|(MoS.+\d+|MoS\d+)|(MoSe.+\d+|MoSe\d+)|(MoTe.+\d+|MoTe\d+)|(WS.+\d+|WS\d+)|(WSe.+\d+|WSe\d+)|(WTe.+\d+|WTe\d+)|(Bi\d+Rh\d+I\d+|Bi.+\d+.+Rh.+\d+.+I.+\d+.+)|(BiTeI)|(BiTeBr)|(BiTeCl)|(ZrTe5|ZrTe.+5)|(Pt2HgSe3|Pt.+2HgSe.+3)|(jacuting[a-z]+)|(flatband)|(flat.{1}band)|(LK.{1}99)

Influence of interlayer exchange coupling on ultrafast laser-induced magnetization reversal in ferromagnetic spin valves
Junta Igarashi, Yann Le Guen, Julius Hohlfeld, Stéphane Mangin, Jon Gorchon, Michel Hehn, and Grégory Malinowski
Author(s): Junta Igarashi, Yann Le Guen, Julius Hohlfeld, Stéphane Mangin, Jon Gorchon, Michel Hehn, and Grégory Malinowski

In this study, we explore the influence of interlayer exchange coupling on magnetization reversal triggered by femtosecond laser pulses in ferromagnetic spin valves. Our experiments, focused on femtosecond laser-induced magnetization reversal, methodically vary the thickness of the copper (Cu) space…


[Phys. Rev. B 109, 094422] Published Mon Mar 18, 2024

Effects of intralayer correlations on electron-hole double-layer superfluidity
Filippo Pascucci, Sara Conti, Andrea Perali, Jacques Tempere, and David Neilson
Author(s): Filippo Pascucci, Sara Conti, Andrea Perali, Jacques Tempere, and David Neilson

We investigate the intralayer correlations acting within the layers in a superfluid system of electron-hole spatially separated layers. In this system, superfluidity is predicted to be almost exclusively confined to the Bose-Einstein condensate (BEC) and crossover regimes where the electron-hole pai…


[Phys. Rev. B 109, 094512] Published Mon Mar 18, 2024

Ginzburg-Landau approach to the vortex–domain wall interaction in superconductors with nematic order
R. S. Severino, P. D. Mininni, E. Fradkin, V. Bekeris, G. Pasquini, and G. S. Lozano
Author(s): R. S. Severino, P. D. Mininni, E. Fradkin, V. Bekeris, G. Pasquini, and G. S. Lozano

In this work, we study the interaction between vortices and nematic domain walls within the framework of a Ginzburg-Landau approach. The free energy of the system is written in terms of a complex order parameter characteristic of $s$-wave superconductivity and a real (Ising-type) order parameter ass…


[Phys. Rev. B 109, 094513] Published Mon Mar 18, 2024

Higher-order topological corner and bond-localized modes in magnonic insulators
Sayak Bhowmik, Saikat Banerjee, and Arijit Saha
Author(s): Sayak Bhowmik, Saikat Banerjee, and Arijit Saha

We theoretically investigate a two-dimensional decorated honeycomb lattice framework to realize a second-order topological magnon insulator (SOTMI) phase featuring distinct corner-localized modes. Our study emphasizes the pivotal role of spin-magnon mapping in characterizing bosonic topological prop…


[Phys. Rev. B 109, 104417] Published Mon Mar 18, 2024

Magnetism and superconductivity in mixed-dimensional periodic Anderson model for ${\mathrm{UTe}}_{2}$
Ryuji Hakuno, Kosuke Nogaki, and Youichi Yanase
Author(s): Ryuji Hakuno, Kosuke Nogaki, and Youichi Yanase

${\mathrm{UTe}}_{2}$ is a strong candidate for a topological spin-triplet superconductor, and it is considered that the interplay of magnetic fluctuation and superconductivity is essential for the origin of the superconductivity. Despite various experiments suggesting ferromagnetic criticality, neut…


[Phys. Rev. B 109, 104509] Published Mon Mar 18, 2024

Kekulé valence bond order in the Hubbard model on the honeycomb lattice with possible lattice distortions for graphene
Yuichi Otsuka and Seiji Yunoki
Author(s): Yuichi Otsuka and Seiji Yunoki

We investigate if and how the valence-bond-solid (VBS) state emerges in the Hubbard model on the honeycomb lattice when the Peierls-type electron-lattice coupling is introduced. We consider all possible lattice-distortion patterns allowed for this lattice model for graphene which preserve the reflec…


[Phys. Rev. B 109, 115131] Published Mon Mar 18, 2024

Finite-temperature entanglement negativity of fermionic symmetry-protected topological phases and quantum critical points in one dimension
Wonjune Choi, Michael Knap, and Frank Pollmann
Author(s): Wonjune Choi, Michael Knap, and Frank Pollmann

We study the logarithmic entanglement negativity of symmetry-protected topological (SPT) phases and quantum critical points (QCPs) of one-dimensional noninteracting fermions at finite temperatures. In particular, we consider a free fermion model that realizes not only quantum phase transitions betwe…


[Phys. Rev. B 109, 115132] Published Mon Mar 18, 2024

Phononic hybrid-order topology in semihydrogenated graphene
Wangping Liu, Zhong-Ke Ding, Nannan Luo, Jiang Zeng, Li-Ming Tang, and Ke-Qiu Chen
Author(s): Wangping Liu, Zhong-Ke Ding, Nannan Luo, Jiang Zeng, Li-Ming Tang, and Ke-Qiu Chen

In recent years, first-order and second-order topological phonons have been discovered in crystalline materials, which has aroused great interest. In the present work, through symmetry analysis and bulk polarization calculation, we demonstrate that semihydrogenated graphene (i.e., graphone) is an id…


[Phys. Rev. B 109, 115422] Published Mon Mar 18, 2024

Wannier charge center, spin resolved bulk polarization, and corner modes in a strained quantum spin Hall insulator
Srijata Lahiri and Saurabh Basu
Author(s): Srijata Lahiri and Saurabh Basu

Topological invariants are a significant ingredient in the study of topological phases of matter that intertwines the supposedly contradicting concepts of bulk and boundary. The nature of the invariants differs depending on the dimensionality of the boundary at which the topologically nontrivial sta…


[Phys. Rev. B 109, 115424] Published Mon Mar 18, 2024

Delocalization in a partially disordered interacting many-body system
Suman Mondal and Fabian Heidrich-Meisner
Author(s): Suman Mondal and Fabian Heidrich-Meisner

We study a partially disordered one-dimensional system with interacting particles. Concretely, we impose a disorder potential to only every other site, followed by a clean site. Our numerical analysis of eigenstate properties is based on the entanglement entropy and density distributions. Most impor…


[Phys. Rev. B 109, 125127] Published Mon Mar 18, 2024

Effect of trivial bands on chiral anomaly induced longitudinal magnetoconductivity in Weyl semimetals
Jeonghyeon Suh and Hongki Min
Author(s): Jeonghyeon Suh and Hongki Min

Including the effect of the trivial band near Weyl nodes, we evaluate the longitudinal magnetoconductivity (LMC) of Weyl semimetals along the magnetic field direction using the Boltzmann magnetotransport theory and study its dependence on the magnetic field, Fermi energy, and temperature. We find th…


[Phys. Rev. B 109, 125128] Published Mon Mar 18, 2024

Ferroelectric topological superconductor: $α\text{−}{\mathrm{In}}_{2}{\mathrm{Se}}_{3}$
Xiaoming Zhang, Pei Zhao, and Feng Liu
Author(s): Xiaoming Zhang, Pei Zhao, and Feng Liu

A two-dimensional topological superconductor (TSC) represents an exotic quantum material with quasiparticle excitation manifesting in dispersive Majorana modes (DMMs) at the boundaries. A domain-wall DMM can arise at the boundary between two TSC domains with opposite Chern numbers or with a π-phase …


[Phys. Rev. B 109, 125130] Published Mon Mar 18, 2024

Detection of the chirality of twisted bilayer graphene by the optical absorption
Xin-Miao Qiu, Ning Yang, Weidong Chu, and Jie-Yun Yan
Author(s): Xin-Miao Qiu, Ning Yang, Weidong Chu, and Jie-Yun Yan

Twisted bilayer graphene possesses intrinsic chirality, which has received less attention among the extensive research conducted on twistronics. In this paper, the optical absorption theory beyond the common linear perturbation is developed with more sophisticated light-electron interactions conside…


[Phys. Rev. B 109, 125419] Published Mon Mar 18, 2024

Electrical resistance associated with the scattering of optically oriented spin-polarized electrons in $n$-GaAs
M. D. Ragoza, N. V. Kozyrev, S. V. Nekrasov, B. R. Namozov, Yu. G. Kusrayev, N. Bart, A. Ludwig, and A. D. Wieck
Author(s): M. D. Ragoza, N. V. Kozyrev, S. V. Nekrasov, B. R. Namozov, Yu. G. Kusrayev, N. Bart, A. Ludwig, and A. D. Wieck

In a bulk GaAs crystal, an unusual magnetoresistance effect, which takes place when a spin-polarized current flows through the sample, was detected. Under conditions of optical pumping of electron spins, an external magnetic field directed along the electric current and perpendicular to the oriented…


[Phys. Rev. B 109, L121203] Published Mon Mar 18, 2024

Wigner-molecule supercrystal in transition metal dichalcogenide moiré superlattices: Lessons from the bottom-up approach
Constantine Yannouleas and Uzi Landman
Author(s): Constantine Yannouleas and Uzi Landman

The few-body problem for $N=4$ fermionic charge carriers in a double-well moiré quantum dot (MQD), representing the first step in a bottom-up strategy to investigate formation of molecular supercrystals in transition metal dichalcogenide (TMD) moiré superlattices with integral fillings, $ν>1$, is…


[Phys. Rev. B 109, L121302] Published Mon Mar 18, 2024

Dynamical Majorana Ising spin response in a topological superconductor–magnet hybrid by microwave irradiation
Yuya Ominato, Ai Yamakage, and Mamoru Matsuo
Author(s): Yuya Ominato, Ai Yamakage, and Mamoru Matsuo

We study a dynamical spin response of surface Majorana modes in a topological superconductor–magnet hybrid under microwave irradiation. We find a method to toggle between dissipative and nondissipative Majorana Ising spin dynamics by adjusting the external magnetic field angle and the microwave freq…


[Phys. Rev. B 109, L121405] Published Mon Mar 18, 2024

Found 1 papers in prl
Date of feed: Tue, 19 Mar 2024 04:17:06 GMT

Search terms: (topolog[a-z]+)|(graphit[a-z]+)|(rhombohedr[a-z]+)|(graphe[a-z]+)|(chalcog[a-z]+)|(landau)|(weyl)|(dirac)|(STM)|(scan[a-z]+ tunne[a-z]+ micr[a-z]+)|(scan[a-z]+ tunne[a-z]+ spectr[a-z]+)|(scan[a-z]+ prob[a-z]+ micr[a-z]+)|(MoS.+\d+|MoS\d+)|(MoSe.+\d+|MoSe\d+)|(MoTe.+\d+|MoTe\d+)|(WS.+\d+|WS\d+)|(WSe.+\d+|WSe\d+)|(WTe.+\d+|WTe\d+)|(Bi\d+Rh\d+I\d+|Bi.+\d+.+Rh.+\d+.+I.+\d+.+)|(BiTeI)|(BiTeBr)|(BiTeCl)|(ZrTe5|ZrTe.+5)|(Pt2HgSe3|Pt.+2HgSe.+3)|(jacuting[a-z]+)|(flatband)|(flat.{1}band)|(LK.{1}99)

Topological Flat Bands in Graphene Super-Moiré Lattices
Mohammed M. Al Ezzi, Junxiong Hu, Ariando Ariando, Francisco Guinea, and Shaffique Adam
Author(s): Mohammed M. Al Ezzi, Junxiong Hu, Ariando Ariando, Francisco Guinea, and Shaffique Adam

A super-moiré lattice in monolayer graphene generates flat bands, providing a viable platform to engineer its correlated states.


[Phys. Rev. Lett. 132, 126401] Published Mon Mar 18, 2024

Found 2 papers in pr_res
Date of feed: Tue, 19 Mar 2024 04:17:06 GMT

Search terms: (topolog[a-z]+)|(graphit[a-z]+)|(rhombohedr[a-z]+)|(graphe[a-z]+)|(chalcog[a-z]+)|(landau)|(weyl)|(dirac)|(STM)|(scan[a-z]+ tunne[a-z]+ micr[a-z]+)|(scan[a-z]+ tunne[a-z]+ spectr[a-z]+)|(scan[a-z]+ prob[a-z]+ micr[a-z]+)|(MoS.+\d+|MoS\d+)|(MoSe.+\d+|MoSe\d+)|(MoTe.+\d+|MoTe\d+)|(WS.+\d+|WS\d+)|(WSe.+\d+|WSe\d+)|(WTe.+\d+|WTe\d+)|(Bi\d+Rh\d+I\d+|Bi.+\d+.+Rh.+\d+.+I.+\d+.+)|(BiTeI)|(BiTeBr)|(BiTeCl)|(ZrTe5|ZrTe.+5)|(Pt2HgSe3|Pt.+2HgSe.+3)|(jacuting[a-z]+)|(flatband)|(flat.{1}band)|(LK.{1}99)

Quantum interference between distant creation processes
Johannes Pseiner, Manuel Erhard, and Mario Krenn
Author(s): Johannes Pseiner, Manuel Erhard, and Mario Krenn

The search for macroscopic quantum phenomena is a fundamental pursuit in quantum mechanics. It allows us to test the limits of quantum physics and provides new avenues for exploring the interplay between quantum mechanics and relativity. In this work, we introduce a novel approach to generate macros…


[Phys. Rev. Research 6, 013294] Published Mon Mar 18, 2024

Effects of noise on the overparametrization of quantum neural networks
Diego García-Martín, Martín Larocca, and M. Cerezo
Author(s): Diego García-Martín, Martín Larocca, and M. Cerezo

Overparametrization is one of the most surprising and notorious phenomena in machine learning. Recently, there have been several efforts to study if, and how, quantum neural networks (QNNs) acting in the absence of hardware noise can be overparametrized. In particular, it has been proposed that a QN…


[Phys. Rev. Research 6, 013295] Published Mon Mar 18, 2024

Found 2 papers in acs-nano
Date of feed: Mon, 18 Mar 2024 13:05:20 GMT

Search terms: (topolog[a-z]+)|(graphit[a-z]+)|(rhombohedr[a-z]+)|(graphe[a-z]+)|(chalcog[a-z]+)|(landau)|(weyl)|(dirac)|(STM)|(scan[a-z]+ tunne[a-z]+ micr[a-z]+)|(scan[a-z]+ tunne[a-z]+ spectr[a-z]+)|(scan[a-z]+ prob[a-z]+ micr[a-z]+)|(MoS.+\d+|MoS\d+)|(MoSe.+\d+|MoSe\d+)|(MoTe.+\d+|MoTe\d+)|(WS.+\d+|WS\d+)|(WSe.+\d+|WSe\d+)|(WTe.+\d+|WTe\d+)|(Bi\d+Rh\d+I\d+|Bi.+\d+.+Rh.+\d+.+I.+\d+.+)|(BiTeI)|(BiTeBr)|(BiTeCl)|(ZrTe5|ZrTe.+5)|(Pt2HgSe3|Pt.+2HgSe.+3)|(jacuting[a-z]+)|(flatband)|(flat.{1}band)|(LK.{1}99)

[ASAP] Solid Electrolyte Interphase Recombination on Graphene Nanoribbons for Lithium Anode
Xiaowei Shi, Jiamei Liu, Huandi Zhang, Zhuangzhuang Xue, Zehua Zhao, Yan Zhang, Guolong Wang, Lubna Akbar, and Lei Li

TOC Graphic

ACS Nano
DOI: 10.1021/acsnano.3c11796

[ASAP] Tuning the Fermi Level of Graphene by Two-Dimensional Metals for Raman Detection of Molecules
Na Zhang, Kunyan Zhang, Min Zou, Rinu Abraham Maniyara, Timothy Andrew Bowen, Jonathon Ray Schrecengost, Arpit Jain, Da Zhou, Chengye Dong, Zhuohang Yu, He Liu, Noel C. Giebink, Joshua A. Robinson, Wei Hu, Shengxi Huang, and Mauricio Terrones

TOC Graphic

ACS Nano
DOI: 10.1021/acsnano.3c12152

Found 1 papers in nat-comm


Search terms: (topolog[a-z]+)|(graphit[a-z]+)|(rhombohedr[a-z]+)|(graphe[a-z]+)|(chalcog[a-z]+)|(landau)|(weyl)|(dirac)|(STM)|(scan[a-z]+ tunne[a-z]+ micr[a-z]+)|(scan[a-z]+ tunne[a-z]+ spectr[a-z]+)|(scan[a-z]+ prob[a-z]+ micr[a-z]+)|(MoS.+\d+|MoS\d+)|(MoSe.+\d+|MoSe\d+)|(MoTe.+\d+|MoTe\d+)|(WS.+\d+|WS\d+)|(WSe.+\d+|WSe\d+)|(WTe.+\d+|WTe\d+)|(Bi\d+Rh\d+I\d+|Bi.+\d+.+Rh.+\d+.+I.+\d+.+)|(BiTeI)|(BiTeBr)|(BiTeCl)|(ZrTe5|ZrTe.+5)|(Pt2HgSe3|Pt.+2HgSe.+3)|(jacuting[a-z]+)|(flatband)|(flat.{1}band)|(LK.{1}99)

Ultrafast magnetization enhancement via the dynamic spin-filter effect of type-II Weyl nodes in a kagome ferromagnet
< author missing >

Found 1 papers in comm-phys


Search terms: (topolog[a-z]+)|(graphit[a-z]+)|(rhombohedr[a-z]+)|(graphe[a-z]+)|(chalcog[a-z]+)|(landau)|(weyl)|(dirac)|(STM)|(scan[a-z]+ tunne[a-z]+ micr[a-z]+)|(scan[a-z]+ tunne[a-z]+ spectr[a-z]+)|(scan[a-z]+ prob[a-z]+ micr[a-z]+)|(MoS.+\d+|MoS\d+)|(MoSe.+\d+|MoSe\d+)|(MoTe.+\d+|MoTe\d+)|(WS.+\d+|WS\d+)|(WSe.+\d+|WSe\d+)|(WTe.+\d+|WTe\d+)|(Bi\d+Rh\d+I\d+|Bi.+\d+.+Rh.+\d+.+I.+\d+.+)|(BiTeI)|(BiTeBr)|(BiTeCl)|(ZrTe5|ZrTe.+5)|(Pt2HgSe3|Pt.+2HgSe.+3)|(jacuting[a-z]+)|(flatband)|(flat.{1}band)|(LK.{1}99)

Time-dependent Gutzwiller simulation of Floquet topological superconductivity
Sota Kitamura

Communications Physics, Published online: 16 March 2024; doi:10.1038/s42005-024-01586-w

Light-matter interaction provides advanced solutions to engineer quantum phases of matter. The authors unveil the emergence of a topological gap in superconductors when circularly polarized light impinges on the material, thereby disclosing accessible strategies to implement novel quantum technologies.