Found 40 papers in cond-mat

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Interaction-driven Roton Condensation in C = 2/3 Fractional Quantum Anomalous Hall State
Hongyu Lu, Han-Qing Wu, Bin-Bin Chen, Kai Sun, Zi Yang Meng
arXiv:2403.03258v1 Announce Type: new Abstract: The interplay of topological order and charge order exhibits rich physics. Recent experiments that succesfully realized the frational quantum anomalous Hall (FQAH) effect in twisted MoTe$_2$ bilayers and rhombohedral multilayer graphene without external magnetic field further call for deeper understanding of the relation between topological order and charge order in quantum moir\'e materials. In the archetypal correlated flat-band model on checkerboard lattice, a FQAH smectic state with coexistent topological order and smectic charge order has been numerically discovered at filling $\nu$ = 2/3. In this work, we explore the global ground-state phase diagram of the model with competing interactions and find a C = 2/3 FQAH phase surrounded by four different charge density wave (CDW) phases. In particular, we identify a FQAH-CDW transition triggered by roton condensation, in that, the minimal roton gap continues to decrease at the same finite momentum, along with the diverging density flucuations at the transition point, after which the system enters into a CDW metal phase with the same ordered wavevector. Our discovery points out that the charge-neutral roton modes can play a significant role in a transition from FQAH topological order to CDW symmetry-breaking order, discussed in FQH literature while severely neglected in FQAH systems.

Observation of Chiral Surface State in Superconducting NbGe$_2$
Mengyu Yao, Martin Guierrez-Amigo, Subhajit Roychowdhury, Ion Errea, Alexander Fedorov, Vladimir N. Strocov, Maia G. Vergniory, Claudia Felser
arXiv:2403.03324v1 Announce Type: new Abstract: The interplay between topology and superconductivity in quantum materials harbors rich physics ripe for discovery. In this study, we investigate the topological properties and superconductivity of the nonsymmorphic chiral superconductor NbGe$_2$ using high-resolution angle-resolved pho-toemission spectroscopy (ARPES), transport measurements, and ab initio calculations. The ARPES data revealed exotic chiral surface states on the (100) surface originating from the inherent chiral crystal structure. Supporting calculations indicate that NbGe$_2$ likely hosts elusive Weyl fermions in its bulk electronic structure. Furthermore, we uncovered the signatures of van Hove singularities that can enhance many-body interactions. Additionally, transport measurements demonstrated that NbGe$_2$ exhibits superconductivity below 2K. Overall, our comprehensive results provide the first concrete evidence that NbGe$_2$ is a promising platform for investigating the interplay between non-trivial band topology, possible Weyl fermions, van Hove singularities, and superconductivity in chiral quantum materials.

Relating the Hall conductivity to the many-body Chern number using Fermi's Golden rule and Kramers-Kronig relations
Nathan Goldman, Tomoki Ozawa
arXiv:2403.03340v1 Announce Type: new Abstract: This pedagogical piece provides a surprisingly simple demonstration that the quantized Hall conductivity of correlated insulators is given by the many-body Chern number, a topological invariant defined in the space of twisted boundary conditions. In contrast to conventional proofs, generally based on the Kubo formula, our approach entirely relies on combining Kramers-Kronig relations and Fermi's golden rule within a circular-dichroism framework. This pedagogical derivation illustrates how the Hall conductivity of correlated insulators can be determined by monitoring single-particle excitations upon a circular drive, a conceptually simple picture with direct implications for quantum-engineered systems, where excitation rates can be directly monitored.

Two-dimensional Kagome-in-Honeycomb materials (MN$_4$)$_3$C$_{32}$ (M=Pt or Mn)
Jingping Dong, Miao Gao, Xun-Wang Yan, Fengjie Ma, Zhong-Yi Lu
arXiv:2403.03402v1 Announce Type: new Abstract: We propose two novel two-dimensional (2D) topological materials, (PtN$_4$)$_3$C$_{32}$ and (MnN$_4$)$_3$C$_{32}$, with a special geometry that we named as kagome-in-honeycomb (KIH) lattice structure, to illustrate the coexistence of the paradigmatic states of kagome physics, Dirac fermions and flat bands, that are difficult to be simultaneously observed in three-dimensional realistic systems. In such system, MN$_4$(M=Pt or Mn) moieties are embedded in honeycomb graphene sheet according to kagome lattice structure, thereby resulting in a KIH lattice. Using the first-principles calculations, we have systemically studied the structural, electronic, and topological properties of these two materials. In the absence of spin-orbit coupling (SOC), they both exhibit the coexistence of Dirac/quadratic-crossing cone and flat band near the Fermi level. When SOC is included, a sizable topological gap is opened at the Dirac/quadratic-crossing nodal point. For nonmagnetic (PtN$_4$)$_3$C$_{32}$, the system is converted into a $\mathbb{Z}_2$ topological quantum spin Hall insulator defined on a curved Fermi level, while for ferromagnetic (MnN$_4$)$_3$C$_{32}$, the material is changed from a half-semi-metal to a quantum anomalous Hall insulator with nonzero Chern number and nontrivial chiral edge states. Our findings not only predict a new family of 2D quantum materials, but also provide an experimentally feasible platform to explore the emergent kagome physics, topological quantum Hall physics, strongly correlated phenomena, and theirs fascinating applications.

Johnson-noise-limited cancellation-free microwave impedance microscopy with monolithic silicon cantilever probes
Jun-Yi Shan, Nathaniel Morrison, Su-Di Chen, Feng Wang, Eric Y. Ma
arXiv:2403.03423v1 Announce Type: new Abstract: Microwave impedance microscopy (MIM) is an emerging scanning probe technique for nanoscale complex permittivity mapping and has made significant impacts in diverse fields from semiconductors to quantum materials. To date, the most significant hurdles that limit its widespread use are the requirements of specialized microwave probes and high-precision cancellation circuits. Here we show that forgoing both elements not only is feasible but actually enhances MIM performance. Using monolithic silicon cantilever probes and a cancellation-free architecture, we demonstrate thermal Johnson-noise-limited, drift-free MIM operation with 15 nm spatial resolution, minimal topography crosstalk, and an unprecedented sensitivity of 0.26 zF/$\sqrt{\text{Hz}}$. We accomplish this by taking advantage of the high mechanical resonant frequency and spatial resolution of silicon probes, the inherent common-mode phase noise rejection of self-referenced homodyne detection, and the exceptional stability of the streamlined architecture. Our approach makes MIM drastically more accessible and paves the way for more advanced operation modes and integration with complementary techniques.

Observation of counterflow superfluidity in a two-component Mott insulator
Yong-Guang Zheng, An Luo, Ying-Chao Shen, Ming-Gen He, Zi-Hang Zhu, Ying Liu, Wei-Yong Zhang, Hui Sun, Youjin Deng, Zhen-Sheng Yuan, Jian-Wei Pan
arXiv:2403.03479v1 Announce Type: new Abstract: The counterflow superfluidity (CSF) was predicted two decades ago. Counterintuitively, while both components in the CSF have fluidity, their correlated counterflow currents cancel out leading the overall system to an incompressible Mott insulator. However, realizing and identifying the CSF remain challenging due to the request on extreme experimental capabilities in a single setup. Here, we observe the CSF in a binary Bose mixture in optical lattices. We prepare a low-entropy spin-Mott state by conveying and merging two spin-1/2 bosonic atoms at every site and drive it adiabatically to the CSF at $\sim$ 1 nK. Antipair correlations of the CSF are probed though a site- and spin-resolved quantum gas microscope in both real and momentum spaces. These techniques and observations provide accessibility to the symmetry-protected topological quantum matters.

Impurities, or dopants, that is the question
Baptiste Gault, Leonardo Shoji Aota, Mathias Kr\"amer, Se-Ho Kim
arXiv:2403.03480v1 Announce Type: new Abstract: The numerous stories around LK-99 as a possible room-temperature superconductor over the summer of 2023 epitomise that materials are more than a bulk crystallographic structure or an expected composition. Like all materials, those at the core of technologies for the energy generation transition, including batteries, catalysts or quantum materials draw their properties from a hierarchy of microstructural features where impurities can dramatically influence the outcomes. As we move towards a circular economy, the recycling of materials will inevitably create fluxes of increasingly impure materials, generating new challenges for fabricating materials with controlled properties. Here, we provide our perspective on how high-end microscopy and microanalysis have helped us to understand relationships between synthesis, processing and microstructure, avoiding imprecise or even erroneous interpretations on the origins of the properties from a range of materials. We highlight examples of how unexpected impurities and their spatial distribution on the nanoscale can be turned into an advantage to define pathways for synthesis of materials with new and novel sets of physical properties.

Tracing Dirac points of topological surface states by ferromagnetic resonance
Laura Pietanesi, Magdalena Marganska, Thomas Mayer, Michael Barth, Lin Chen, Ji Zou, Adrian Weindl, Alexander Liebig, Rebeca D\'iaz-Pardo, Dhavala Suri, Florian Schmid, Franz J. Gie{\ss}ibl, Klaus Richter, Yaroslav Tserkovnyak, Matthias Kronseder, Christian H. Back
arXiv:2403.03518v1 Announce Type: new Abstract: Ferromagnetic resonance is used to reveal features of the buried electronic band structure at interfaces between ferromagnetic metals and topological insulators. By monitoring the evolution of magnetic damping, the application of this method to a hybrid structure consisting of a ferromagnetic layer and a 3D topological insulator reveals a clear fingerprint of the Dirac point and exhibits additional features of the interfacial band structure not otherwise observable. The underlying spin-pumping mechanism is discussed in the framework of dissipation of angular momentum by topological surface states (TSSs). Tuning of the Fermi level within the TSS was verified both by varying the stoichiometry of the topological insulator layer and by electrostatic backgating and the damping values obtained in both cases show a remarkable agreement. The high energy resolution of this method additionally allows us to resolve the energetic shift of the local Dirac points generated by local variations of the electrostatic potential. Calculations based on the chiral tunneling process naturally occurring in TSS agree well with the experimental results.

High-harmonic generation in graphene under the application of a DC electric current: From perturbative to non-perturbative regimes
Minoru Kanega, Masahiro Sato
arXiv:2403.03523v1 Announce Type: new Abstract: We theoretically investigate high-harmonic generation (HHG) in honeycomb-lattice graphene models when subjected to a DC electric field. By integrating the quantum master equation with the Boltzmann equation, we develop a numerical method to compute laser-driven dynamics in many-electron lattice systems under DC electric current. The method enables us to treat both the weak-laser (perturbative) and intense-laser (non-perturbative) regimes in a unified way, accounting for the experimentally inevitable dissipation effects. From it, we obtain the HHG spectra and analyze their dependence on laser frequency, laser intensity, laser-field direction, and DC current strength. We show that the dynamical and static symmetries are partially broken by a DC current or staggered potential term, and such symmetry breakings drastically change the shape of the HHG spectra, especially in terms of the presence or absence of $(2n+1)$-th, $2n$-th, or $3n$-th order harmonics ($n\in \mathbb Z$). The laser intensity, frequency, and polarization are also shown to affect the shape of the HHG spectra. Our findings indicate that HHG spectra in conducting electron systems can be quantitatively or qualitatively controlled by tuning various external parameters, and DC electric current is used as such an efficient parameter.

Weyl points and anomalous transport effects tuned by the Fe doping in Mn$_3$Ge Weyl semimetal
Venus Rai, Subhadip Jana, J\"org Per{\ss}on, Shibabrata Nandi
arXiv:2403.03626v1 Announce Type: new Abstract: The discovery of a significantly large anomalous Hall effect in the chiral antiferromagnetic system - Mn$_3$Ge - indicates that the Weyl points are widely separated in phase space and positioned near the Fermi surface. In order to examine the effects of Fe substitution in Mn$_3$Ge on the presence and location of the Weyl points, we synthesized (Mn$_{1-\alpha}$Fe$_{\alpha})$$_3$Ge ($\alpha=0-0.30$) compounds. The anomalous Hall effect was observed in compounds up to $\alpha=0.22$, but only within the temperature range where the magnetic structure remains the same as the Mn$_3$Ge. Additionally, positive longitudinal magnetoconductance and planar Hall effect were detected within the same temperature and doping range. These findings strongly suggest the existence of Weyl points in (Mn$_{1-\alpha}$Fe$_{\alpha})$$_3$Ge ($\alpha=0-0.22$) compounds. Further, we observed that with an increase in Fe doping fraction, there is a significant reduction in the magnitude of anomalous Hall conductivity, planar Hall effect, and positive longitudinal magnetoconductance, indicating that the Weyl points move further away from the Fermi surface. Consequently, it can be concluded that suitable dopants in the parent Weyl semimetals have the potential to tune the properties of Weyl points and the resulting anomalous electrical transport effects.

Crystal, ferromagnetism, and magnetoresistance with sign reversal in a EuAgP semiconductor
Qian Zhao, Kaitong Sun, Si Wu, Hai-Feng Li
arXiv:2403.03650v1 Announce Type: new Abstract: We synthesized the ferromagnetic EuAgP semiconductor and conducted a comprehensive study of its crystalline, magnetic, heat capacity, band gap, and magnetoresistance properties. Our investigation utilized a combination of X-ray diffraction, optical, and PPMS DynaCool measurements. EuAgP adopts a hexagonal structure with the $P6_3/mmc$ space group. As the temperature decreases, it undergoes a magnetic phase transition from high-temperature paramagnetism to low-temperature ferromagnetism. We determined the ferromagnetic transition temperature to be $T_{\textrm{C}} =$ 16.45(1) K by fitting the measured magnetic susceptibility using a Curie-Weiss law. Heat capacity analysis of EuAgP considered contributions from electrons, phonons, and magnons, revealing $\eta$ = 0.03 J/mol/$\textrm{K}^\textrm{2}$, indicative of semiconducting behavior. Additionally, we calculated a band gap of $\sim$ 1.324(4) eV based on absorption spectrum measurements. The resistivity versus temperature of EuAgP measured in the absence of an applied magnetic field shows a pronounced peak around $T_{\textrm{C}}$, which diminishes rapidly with increasing applied magnetic fields, ranging from 1 to 14 T. An intriguing phenomenon emerges in the form of a distinct magnetoresistance transition, shifting from positive (e.g., 1.95\% at 300 K and 14 T) to negative (e.g., -30.73\% at 14.25 K and 14 T) as the temperature decreases. This behavior could be attributed to spin-disordered scattering.

Revisiting phonon thermal transport in two-dimensional gallium nitride: higher-order phonon-phonon and phonon-electron scattering
Jianshi Sun, Xiangjun Liu, Yucheng Xiong, Yuhang Yao, Xiaolong Yang, Cheng Shao, Shouhang Li
arXiv:2403.03673v1 Announce Type: new Abstract: Two-dimensional gallium nitride (2D-GaN) has great potential in power electronics and optoelectronics. Heat dissipation is a critical issue for these applications of 2D-GaN. Previous studies showed that higher-order phonon-phonon scattering has extremely strong effects on the lattice thermal conductivity of 2D-GaN, which exhibits noticeable discrepancies with lattice thermal conductivity calculated from molecular dynamics. In this work, it is found that the fourth-order interatomic force constants (4th-IFCs) of 2D-GaN are quite sensitive to atomic displacement in the finite different method. The effects of the four-phonon scattering can be severely overestimated with non-convergent 4th-IFCs. The lattice thermal conductivity from three-phonon scattering is reduced by 65.6% due to four-phonon scattering. The reflection symmetry allows significantly more four-phonon processes than three-phonon processes. It was previously thought the electron-phonon interactions have significant effects on the lattice thermal conductivity of two-dimensional materials. However, the effects of phonon-electron interactions on the lattice thermal conductivity of both n-type and p-type 2D-GaN at high charge carrier concentrations can be neglected due to the few phonon-electron scattering channels and the relatively strong four-phonon scattering.

Quantum phase transition between topologically distinct quantum critical points
Xue-Jia Yu, Wei-Lin Li
arXiv:2403.03716v1 Announce Type: new Abstract: By constructing an exactly solvable spin model, we investigate the critical behaviors of transverse field Ising chains interpolated with cluster interactions, which exhibit various types of topologically distinct Ising critical points. Using fidelity susceptibility as an indicator, we establish the global phase diagram, including ferromagnetic, trivial paramagnetic, and symmetry-protected topological phases. Different types of critical points exist between these phases, encompassing both topologically trivial and non-trivial Ising critical points, as well as Gaussian critical points. Importantly, we demonstrate the existence of a Lifshitz transition between these topologically distinct Ising critical points, with central charge and critical exponents determined through finite-size scaling. This work serves as a valuable reference for further research on phase transitions within the gapless quantum phase of matter.

Case studies on time-dependent Ginzburg-Landau simulations for superconducting applications
Cun Xue, Qing-Yu Wang, Han-Xi Ren, An He, A. V. Silhanek
arXiv:2403.03729v1 Announce Type: new Abstract: The macroscopic electromagnetic properties of type II superconductors are primarily influenced by the behavior of microscopic superconducting flux quantum units. Time-dependent Ginzburg-Landau (TDGL) equations provide an elegant and powerful tool for describing and examining both the statics and dynamics of these superconducting entities. They have been instrumental in replicating and elucidating numerous experimental results over the past decades.This paper provides a comprehensive overview of the progress in TDGL simulations, focusing on three key aspects of superconductor applications. The initial section delves into vortex rectification in superconductors described within the TDGL framework. We specifically highlight the superconducting diode effect achieved through asymmetric pinning landscapes and the reversible manipulation of vortex ratchets with dynamic pinning landscapes. The subsequent section reviews the achievements of TDGL simulations concerning the critical current density of superconductors, emphasizing the optimization of pinning sites, particularly vortex pinning and dynamics in polycrystalline Nb$_3$Sn with grain boundaries. The third part concentrates on numerical modeling of vortex penetration and dynamics in superconducting radio frequency (SRF) cavities, including a discussion of superconductor insulator superconductor multilayer structures. In the last section, we present key findings, insights, and perspectives derived from the discussed simulations.

Engineering of a Layered Ferromagnet via Graphitization: An Overlooked Polymorph of GdAlSi
Dmitry V. Averyanov, Ivan S. Sokolov, Alexander N. Taldenkov, Oleg E. Parfenov, Konstantin V. Larionov, Pavel B. Sorokin, Oleg A. Kondratev, Andrey M. Tokmachev, Vyacheslav G. Storchak
arXiv:2403.03735v1 Announce Type: new Abstract: Layered magnets are stand-out materials because of their range of functional properties that can be controlled by external stimuli. Regretfully, the class of such compounds is rather narrow, prompting the search for new members. Graphitization - stabilization of layered graphitic structures in the 2D limit - is being discussed for cubic materials. We suggest the phenomenon to extend beyond cubic structures; it can be employed as a viable route to a variety of layered materials. Here, the idea of graphitization is put into practice to produce a new layered magnet, GdAlSi. The honeycomb material, based on graphene-like layers AlSi, is studied both experimentally and theoretically. Epitaxial films of GdAlSi are synthesized on silicon; the critical thickness for the stability of the layered polymorph is around 20 monolayers. Notably, the layered polymorph of GdAlSi demonstrates ferromagnetism stemming from the open 4f-shells of Gd, in contrast to the non-layered, tetragonal polymorph. The ferromagnetism is further supported by electron transport measurements revealing negative magnetoresistance and the anomalous Hall effect. The results show that graphitization can be a powerful tool in the design of functional layered materials.

Non-Abelian anyon statistics through AC conductance of a Majorana interferometer
Andrea Nava, Reinhold Egger, Fabian Hassler, Domenico Giuliano
arXiv:2403.03757v1 Announce Type: new Abstract: Demonstrating the non-Abelian Ising anyon statistics of Majorana zero modes in a physical platform still represents a major open challenge in physics. We here show that the linear low-frequency charge conductance of a Majorana interferometer containing a floating superconducting island can reveal the topological spin of quantum edge vortices. The latter are associated with chiral Majorana fermion edge modes and represent "flying" Ising anyons. We describe possible device implementations and outline how to detect non-Abelian anyon braiding through AC conductance measurements.

The role of interfacial interactions and oxygen vacancies in tuning magnetic anisotropy in LaCrO$_{3}$/LaMnO$_{3}$ heterostructures
Xuanyi Zhang, Athby Al-Tawhid, Padraic Schafer, Zhan Zhang, Divine P. Kumah
arXiv:2403.03764v1 Announce Type: new Abstract: The interplay of lattice, electronic, and spin degrees of freedom at epitaxial complex oxide interfaces provides a route to tune their magnetic ground states. Unraveling the competing contributions is critical for tuning their functional properties. We investigate the relationship between magnetic ordering and magnetic anisotropy and the lattice symmetry, oxygen content, and film thickness in compressively strained LaMnO$_3$/LaCrO$_3$ superlattices. Mn-O-Cr antiferromagnetic superexchange interactions across the heterointerface resulting in a net ferrimagnetic magnetic structure. Bulk magnetometry measurements reveal isotropic in-plane magnetism for as-grown oxygen-deficient thinner thin samples due to equal fractions of orthorhombic a+a-c-, and a-a+c- twin domains. As the superlattice thickness is increased, in-plane magnetic anisotropy emerges as the fraction of the a+a-c- domain increases. On annealing in oxygen, the suppression of oxygen vacancies results in a contraction of the lattice volume, and an orthorhombic to rhombohedral transition leads to isotropic magnetism independent of the film thickness. The complex interactions are investigated using high-resolution synchrotron diffraction and X-ray absorption spectroscopy. These results highlight the role of the evolution of structural domains with film thickness, interfacial spin interactions, and oxygen-vacancy-induced structural phase transitions in tuning the magnetic properties of complex oxide heterostructures.

Nonlinear Landau fan diagram and aperiodic magnetic oscillations in three-dimensional systems
Sunit Das, Suvankar Chakraverty, Amit Agarwal
arXiv:2403.03765v1 Announce Type: new Abstract: Quantum oscillations offer a powerful probe for the geometry and topology of the Fermi surface in metals. Onsager's semiclassical quantization relation governs these periodic oscillations in 1/B, leading to a linear Landau fan diagram. However, higher-order magnetic susceptibility-induced corrections give rise to a generalized Onsager's relation, manifesting in experiments as a nonlinear Landau fan diagram and aperiodic quantum oscillations. Here, we explore the generalized Onsager's relation to three-dimensional (3D) systems to capture the B-induced corrections in the free energy and the Fermi surface. We unravel the manifestation of these corrections in the nonlinear Landau fan diagrams and aperiodic quantum oscillations by deriving the B-dependent oscillation frequency and the generalized Lifshitz-Kosevich equation, respectively. Our theory explains the necessary conditions to observe these fascinating effects and predicts the magnetic field dependence of the cyclotron mass. As a concrete example, we elucidate these effects in a 3D spin-orbit coupled system and extract zero-field magnetic response functions from analytically obtained Landau levels. Our comprehensive study deepens and advances our understanding of aperiodic quantum oscillations.

Ultrafast Band Structure Dynamics in Bulk 1$T$-VSe$_2$
Wibke Bronsch, Manuel Tuniz, Denny Puntel, Alessandro Giammarino, Fulvio Parmigiani, Yang-Hao Chan, Federico Cilento
arXiv:2403.03805v1 Announce Type: new Abstract: Complex materials encompassing different phases of matter can display new photoinduced metastable states differing from those attainable under equilibrium conditions. These states can be realized when energy is injected in the material following a non-equilibrium pathway, unbalancing the unperturbed energy landscape of the material. Guided by the fact that photoemission experiments allow for detailed insights in the electronic band structure of ordered systems, here we study bulk 1$T$-VSe$_2$ in its metallic and charge-density-wave phase by time- and angle-resolved photoelectron spectroscopy. After near-infrared optical excitation, the system shows a net increase of the density of states in the energy range of the valence bands, in the vicinity of the Fermi level, lasting for several picoseconds. We discuss possible origins as band shifts or correlation effects on the basis of a band structure analysis. Our results uncover the possibility of altering the electronic band structure of bulk 1$T$-VSe$_2$ for low excitation fluences, contributing to the understanding of light-induced electronic states.

Electron correlations in the kagome flat band metal $\rm CsCr_3Sb_5$
Fang Xie, Yuan Fang, Ying Li, Yuefei Huang, Lei Chen, Chandan Setty, Shouvik Sur, Boris Yakobson, Roser Valent\'i, Qimiao Si
arXiv:2403.03911v1 Announce Type: new Abstract: Kagome metals offer a unique platform for investigating robust electron-correlation effects because of their lattice geometry, flat bands and multi-orbital nature. In the cases with active flat bands, recent theoretical studies have pointed to a rich phase diagram that contains not only electronic orders but also quantum criticality. $\rm CsCr_3Sb_5$ has emerged as a strong candidate for exploring such new physics. Here, using effective tight-binding models obtained from ab initio calculations, we study the effects of electronic correlations and symmetries on the electronic structure of $\rm CsCr_3 Sb_5$. The effective tight-binding model and Fermi surface comprise multiple Cr-$d$ orbitals and Sb-$p$ orbitals. The introduction of Hubbard-Kanamori interactions leads to orbital-selective band renormalization dominated by the $d_{xz}$ band, concurrently producing emergent flat bands very close to the Fermi level. Our analysis sets the stage for further investigations into the electronic properties of $\rm CsCr_3Sb_5$, including electronic orders, quantum criticality and unconventional superconductivity, which promise to shed much new light into the electronic materials with frustrated lattices and bring about new connections with the correlation physics of a variety of strongly correlated systems.

Effect of Uncorrelated On-site Scalar Potential, and Mass Disorder on Transport of Two-Dimensional Dirac Fermions
Arman Duha, Mario Borunda
arXiv:2403.03914v1 Announce Type: new Abstract: We investigate the transport properties of massive Dirac fermions subjected to uncorrelated scalar potential disorder, and mass disorder. Using a finite difference method, the conductance is calculated for a wide variety of combinations of these two disorder strengths. By calculating the scaling of conductivity with system size we find that, depending on the combination, the system can have an insulating, scale invariant, and metallic behavior. We identify the critical values of these disorder strengths where the phase transitions occur. We study both the zero and nonzero average mass cases to examine the effect of scalar potential disorder on band gap. Our results suggest a suppression of the band gap by the scalar potential disorder.

Collision Cascade-Driven Evolution of Vacancy Defects in Ni-Based Concentrated Solid-Solution Alloys
A. Aligayev, M. Landeiro Dos Reis, A. Chartier, Q. Huang, S. Papanikolaou, F. J. Dominguez-Gutierrez
arXiv:2403.03922v1 Announce Type: new Abstract: Concentrated solid--solution alloys (CSAs) in single--phase form have recently garnered considerable attention owing to their potential for exceptional irradiation resistance. This computational study delves into the intricate interplay of alloying elements on the generation, recombination, and evolution of irradiation-induced defects. Molecular dynamics simulations were conducted for collision cascades at room temperature, spanning a range of primary knock-on atom energies from 1 to 10 keV. The investigation encompasses a series of model crystals, progressing from pure Ni to binary CSAs such as NiFe$_{20}$, NiFe, NiCr$_{20}$, and culminating in the more intricate NiFeCr$_{20}$ CSA. We observe that materials rich in chromium actively facilitate dislocation emissions and induce the nucleation of stacking fault tetrahedra in the proximity of nanovoids, owing to Shockley partial interactions. This result is validated by molecular static simulations, which calculate the surface, vacancy, and defect formation energies. Among various shapes considered, the spherical void proves to be the most stable, followed by the truncated octahedron and octahedron shapes. On the other hand, the tetrahedron cubic shape is identified as the most unstable, and stacking fault tetrahedra exhibit the highest formation energy. Notably, among the materials studied, NiCr$_{20}$ and NiFeCr$_{20}$ CSAs stood out as the sole alloys capable of manifesting this mechanism, mainly observed at high impact energies.

Decoupling the electronic gap from the spin Chern number in disordered higher-order topological insulators
Alexander C. Tyner, Cormac Grindall, J. H. Pixley
arXiv:2403.03957v1 Announce Type: new Abstract: In two-dimensional topological insulators, a disorder induced topological phase transition is typically identified with an Anderson localization transition at the Fermi energy. However, in higher-order, spin-resolved topological insulators it is the spectral gap of the spin-spectrum, in addition to the bulk mobility gap, which protects the non-trivial topology of the ground state. In this work, we show that these two gaps, the bulk electronic and spin gap, evolve distinctly upon introduction of disorder. This decoupling leads to a unique situation in which an Anderson localization transition occurs below the Fermi energy at the topological transition. Furthermore, in the clean limit the bulk-boundary correspondence of such higher-order insulators is dictated by crystalline protected topology, coexisting with the spin-resolved topology. By removing the crystalline symmetry, disorder allows for isolated study of the bulk-boundary correspondence of spin-resolved topology for which we demonstrate the absence of protected edge and corner modes in the Hamiltonian and yet the edge modes in the eigenstates of the projected spin operator survive. Our work shows that a non-zero spin-Chern number, in the absence of a non-trivial $\mathbb{Z}_{2}$ index, does not dictate the existence of protected edge modes, resolving a fundamental question posed in 2009.

Quasiparticle effects in magnetic-field-resilient 3D transmons
J. Krause, G. Marchegiani, L. M. Janssen, G. Catelani, Yoichi Ando, C. Dickel
arXiv:2403.03351v1 Announce Type: cross Abstract: Recent research shows that quasiparticle-induced decoherence of superconducting qubits depends on the superconducting-gap asymmetry originating from the different thicknesses of the top and bottom films in Al/AlO$_x$/Al junctions. Magnetic field is a key tuning knob to investigate this dependence as it can change the superconducting gaps in situ. We present measurements of the parity-switching time of a field-resilient 3D transmon with in-plane field up to 0.41T. At low fields, small parity splitting requires qutrit pulse sequences for parity measurements. We measure a non-monotonic evolution of the parity lifetime with in-plane magnetic field, increasing up to 0.2T, followed by a decrease at higher fields. We demonstrate that the superconducting-gap asymmetry plays a crucial role in the observed behavior. At zero field, the qubit frequency is nearly resonant with the superconducting-gap difference, favoring the energy exchange with the quasiparticles and so enhancing the parity-switching rate. With a higher magnetic field, the qubit frequency decreases and gets detuned from the gap difference, causing the initial increase of the parity lifetime, while photon-assisted qubit transitions increase, producing the subsequent decrease at higher fields. Besides giving a deeper insight into the parity-switching mechanism in conventional transmon qubits, we establish that Al-AlO$_x$-Al JJs could be used in architectures for the parity-readout and manipulation of topological qubits based on Majorana zero modes.

Chemically Tailored Growth of 2D Semiconductors via Hybrid Metal-Organic Chemical Vapor Deposition
Zhepeng Zhang, Lauren Hoang, Marisa Hocking, Jenny Hu, Gregory Zaborski Jr., Pooja Reddy, Johnny Dollard, David Goldhaber-Gordon, Tony F. Heinz, Eric Pop, Andrew J. Mannix
arXiv:2403.03482v1 Announce Type: cross Abstract: Two-dimensional (2D) semiconducting transition-metal dichalcogenides (TMDCs) are an exciting platform for new excitonic physics and next-generation electronics, creating a strong demand to understand their growth, doping, and heterostructures. Despite significant progress in solid-source (SS-) and metal-organic chemical vapor deposition (MOCVD), further optimization is necessary to grow highly crystalline 2D TMDCs with controlled doping. Here, we report a hybrid MOCVD growth method that combines liquid-phase metal precursor deposition and vapor-phase organo-chalcogen delivery to leverage the advantages of both MOCVD and SS-CVD. Using our hybrid approach, we demonstrate WS$_2$ growth with tunable morphologies - from separated single-crystal domains to continuous monolayer films - on a variety of substrates, including sapphire, SiO$_2$, and Au. These WS$_2$ films exhibit narrow neutral exciton photoluminescence linewidths down to 33 meV and room-temperature mobility up to 34 - 36 cm$^2$V$^-$$^1$s$^-$$^1$). Through simple modifications to the liquid precursor composition, we demonstrate the growth of V-doped WS$_2$, MoxW$_1$$_-$$_x$S$_2$ alloys, and in-plane WS$_2$-MoS$_2$ heterostructures. This work presents an efficient approach for addressing a variety of TMDC synthesis needs on a laboratory scale.

Backfiring Bosonisation
Philip Boyle Smith, Yunqin Zheng
arXiv:2403.03953v1 Announce Type: cross Abstract: For a fermionic quantum field theory in $d=1+1$ dimensions, there is a subtle difference between summing over spin structures and gauging $(-1)^F$. If the gravitational anomaly vanishes mod 16, then both operations are equivalent and yield a bosonic theory. But if the gravitational anomaly only vanishes mod 8, then only gauging $(-1)^F$ is allowed, and the result is a fermionic theory. Our goal is to understand in detail how this happens, despite the fact $(-1)^F$ is defined in terms of shifting the spin structure, which would na\"ively suggest that both operations are equivalent. We do this from three perspectives: an abstract view in terms of anomalies, explicit CFT calculations, and a Symmetry TFT perspective. To conclude, we illustrate our results using the heterotic string and the famous self-triality of 8 Majorana-Weyl fermions.

Probing Majorana Bound States via Thermoelectric Transport
Colin Benjamin, R. Das
arXiv:2207.01515v2 Announce Type: replace Abstract: We propose a set of thermoelectric experiments based on Aharonov-Bohm interferometry to probe Majorana bound states (MBS), which are generated in 2D topological insulators (TI) in the presence of superconducting and ferromagnetic correlations via the proximity effect. The existence and nature (coupled or uncoupled) of these MBS can be determined by studying the charge and heat transport, specifically, the behavior of various thermoelectric coefficients like the Seebeck coefficient, Peltier coefficient, thermal conductance, and violations of Wiedemann-Franz law as a function of the Fermi energy and Aharonov-Bohm flux piercing the TI ring with the embedded MBS.

Higher-group symmetry in finite gauge theory and stabilizer codes
Maissam Barkeshli, Yu-An Chen, Po-Shen Hsin, Ryohei Kobayashi
arXiv:2211.11764v3 Announce Type: replace Abstract: A large class of gapped phases of matter can be described by topological finite group gauge theories. In this paper we show how such gauge theories possess a higher-group global symmetry, which we study in detail. We derive the $d$-group global symmetry and its 't Hooft anomaly for topological finite group gauge theories in $(d+1)$ space-time dimensions, including non-Abelian gauge groups and Dijkgraaf-Witten twists. We focus on the 1-form symmetry generated by invertible (Abelian) magnetic defects and the higher-form symmetries generated by invertible topological defects decorated with lower dimensional gauged symmetry-protected topological (SPT) phases. We show that due to a generalization of the Witten effect and charge-flux attachment, the 1-form symmetry generated by the magnetic defects mixes with other symmetries into a higher group. We describe such higher-group symmetry in various lattice model examples. We discuss several applications, including the classification of fermionic SPT phases in (3+1)D for general fermionic symmetry groups, where we also derive a simpler formula for the $[O_5] \in H^5(BG, U(1))$ obstruction that has appeared in prior work. We also show how the $d$-group symmetry is related to fault-tolerant non-Pauli logical gates and a refined Clifford hierarchy in stabilizer codes. We discover new logical gates in stabilizer codes using the $d$-group symmetry, such as a Controlled-Z gate in (3+1)D $\mathbb{Z}_2$ toric code.

Optical Manipulation of the Charge Density Wave state in RbV3Sb5
Yuqing Xing, Seokjin Bae, Ethan Ritz, Fan Yang, Turan Birol, Andrea N. Capa Salinas, Brenden R. Ortiz, Stephen D. Wilson, Ziqiang Wang, Rafael M. Fernandes, Vidya Madhavan
arXiv:2308.04128v2 Announce Type: replace Abstract: Broken time-reversal symmetry in the absence of spin order indicates the presence of unusual phases such as orbital magnetism and loop currents. The recently discovered family of kagome superconductors AV$_3$Sb$_5$ (A = K, Rb, or Cs), hosting an exotic charge-density wave (CDW) state, has emerged as a strong candidate for this phase. While initial experiments suggested that the CDW phase breaks time-reversal symmetry, this idea is being intensely debated due to conflicting experimental data. In this work we use laser-coupled scanning tunneling microscopy (STM) to study RbV$_3$Sb$_5$. STM data shows that the Fourier intensities of all three CDW peaks are different, implying that the CDW breaks rotational and mirror symmetries. By applying linearly polarized light along high-symmetry directions, we show that the relative intensities of the CDW peaks can be reversibly switched, implying a substantial electro-striction response, indicative of strong non-linear electron-phonon coupling. A similar CDW intensity switching is observed with perpendicular magnetic fields, which implies an unusual piezo-magnetic response that, in turn, requires time-reversal symmetry-breaking. We show that the simplest CDW that satisfies these constraints and reconciles previous seemingly contradictory experimental data is an out-of-phase combination of bond charge order and loop currents that we dub congruent CDW flux phase. Our laser-STM data opens the door to the possibility of dynamic optical control of complex quantum phenomenon in correlated materials.

Strong unidirectional Rashba state induced by extended vacancy line defects in a $1T'$-WTe$_{2}$ monolayer
Moh. Adhib Ulil Absor, Harsojo, Iman Santoso
arXiv:2309.13234v2 Announce Type: replace Abstract: The correlation between spin-orbit coupling and low crystal symmetry in the $1T'$ phase of the tungsten ditellurides (WTe$_{2}$) monolayer (ML) plays a significant role in its electronic and topological properties. However, the centrosymmetric nature of the crystal maintains Kramer's spin degeneracy in its electronic states, which limits its functionality in spintronics. In this paper, through a systematic study using first-principles calculations, we show that significant spin splitting can be induced in the $1T'$-WTe$_{2}$ ML by introducing one dimensional (1D) vacancy line defect (VLD). We examine six configurations of the 1D VLD, which consist of three VLDs extended in the armchair direction including a Te$_{1}$ armchair-VLD ($ACV_{\texttt{Te}_{1}}$), Te$_{2}$ armchair-VLD ($ACV_{\texttt{Te}_{2}}$), and W armchair-VLD ($ACV_{\texttt{W}}$); and three VLDs elongated along the zigzag direction comprising a Te$_{1}$ zigzag-VLD ($ZZV_{\texttt{Te}_{1}}$), Te$_{2}$ zigzag-VLD ($ZZV_{\texttt{Te}_{2}}$), and W zigzag-VLD ($ZZV_{\texttt{W}}$), where Te$_{1}$ and Te$_{2}$ are two nonequivalent Te atoms located at the lower and higher sites in the top layer, respectively. We find that both the $ACV_{\texttt{Te}_{1}}$ and $ACV_{\texttt{W}}$ systems have the lowest formation energy. Concerning these two most stable VLD systems, we identify large spin splitting in the defect states near the Fermi level driven by a strong coupling of the in-plane $p-d$ orbitals, displaying highly unidirectional Rashba states with perfectly collinear spin configurations in the momentum space. This unique spin configuration gives rise to a specific spin mode that protects the spin from decoherence and leads to an exceptionally long spin lifetime...........

Chiral Meissner effect in time-reversal invariant Weyl superconductors
Vira Shyta, Jeroen van den Brink, Flavio S. Nogueira
arXiv:2309.14262v2 Announce Type: replace Abstract: Weyl semimetals have nodes in their electronic structure at which electrons attain a definite chirality. Due to the chiral anomaly, the non-conservation of charges with given chirality, the axion term appears in their effective electromagnetic action. We determine how this affects the properties of time-reversal invariant Weyl {\it superconductors} (SCs) in the London regime. For type II SCs the axion coupling generates magnetic $B$-fields transverse to vortices, which become unstable at a critical coupling so that a transition into type I SC ensues. In this regime an applied $B$-field not only decays inside the SC within the London penetration depth, but the axion coupling generates an additional perpendicular field. Consequently, when penetrating into the bulk the $B$-field starts to steadily rotate away from the applied field. At a critical coupling the screening of the magnetic field breaks down. The novel chiral superconducting state that emerges has a periodically divergent susceptibility that separates onsets of chiral Meissner regimes. The chiral anomaly thus leaves very crisp experimental signatures in structurally chiral Weyl SCs with an axion response.

Critical behavior of the dimerized Si(001) surface: Continuous order-disorder phase transition in the two-dimensional Ising universality class
Christian Brand, Alfred Hucht, Hamid Mehdipour, Giriraj Jnawali, Jonas D. Fortmann, Mohammad Tajik, R\"udiger Hild, Bj\"orn Sothmann, Peter Kratzer, Ralf Sch\"utzhold, Michael Horn-von Hoegen
arXiv:2310.10488v4 Announce Type: replace Abstract: The critical behavior of the order-disorder phase transition in the buckled dimer structure of the Si(001) surface is investigated both theoretically by means of first-principles calculations and experimentally by spot profile analysis low-energy electron diffraction (SPA-LEED). We use density functional theory (DFT) with three different functionals commonly used for Si to determine the coupling constants of an effective lattice Hamiltonian describing the dimer interactions. Experimentally, the phase transition from the low-temperature $c(4 {\times} 2)$- to the high-temperature $p(2 {\times} 1)$-reconstructed surface is followed through the intensity and width of the superstructure spots within the temperature range 78-400 K. Near the critical temperature $T_c = 190.6\,\mathrm{K}$, we observe universal critical behavior of spot intensities and correlation lengths which falls into the universality class of the two-dimensional (2D) Ising model. From the ratio of correlation lengths along and across the dimer rows we determine effective nearest-neighbor couplings of an anisotropic 2D Ising model, $J_\parallel = (-24.9 \pm 0.9_\mathrm{stat} \pm 1.3_\mathrm{sys})\,\mathrm{meV}$ and $J_\perp = (-0.8 \pm 0.1_\mathrm{stat})\,\mathrm{meV}$. We find that the experimentally determined coupling constants of the Ising model can be reconciled with those of the more complex lattice Hamiltonian from DFT when the critical behavior is of primary interest. The anisotropy of the interactions derived from the experimental data via the 2D Ising model is best matched by DFT calculations using the PBEsol functional. The trends in the calculated anisotropy are consistent with the surface stress anisotropy predicted by the DFT functionals, pointing towards the role of surface stress reduction as a driving force for establishing the $c(4 {\times} 2)$-reconstructed ground state.

Autoencoder-assisted study of directed percolation with spatial long-range interactions
Yanyang Wang, Yuxiang Yang, Wei Li
arXiv:2311.12426v2 Announce Type: replace Abstract: Spatial L{\'{e}}vy-like flights are introduced as a way in the absorbing phase transitions to produce non-local interactions. We utilize the autoencoder, an unsupervised learning method, to predict the critical points for $(1+1)$-d directed percolation with such spatial long-range interactions. After making a global coverage of the reaction-diffusion distance and taking a series of different values for the parameter ${\beta}$ in the distribution $P(r){\sim}1/r^{\beta}$, the critical points $P_c$ that can be continuously varied are obtained. And the dynamic decay of the particle density under the critical points was counted as a way to determine the critical exponent ${\delta}$ of the survival rate. We also investigate the active behavior of the system's particles under the critical point with increasing time steps, which allows us to determine the characteristic time $t_f$ of the finite-scale systems. And the dynamic exponents $z$ are obtained using the scaling relation $t_f{\sim}L^{z}$. We find that the autoencoder can identify this characteristic evolutionary behavior of particles. Finally, we discuss the compliance of the scaling form $1/{\delta}-({\beta}-2)/{\delta}z=2$ in different ${\beta}$ intervals as well as a method to introduce a global scaling mechanism by generating a random walking step using the L{\'{e}}vy distribution.

Three-dimensional $\mathbb{Z}$ topological insulators without reflection symmetry
Alexander C. Tyner, Vladimir Juri\v{c}i\'c
arXiv:2311.16092v2 Announce Type: replace Abstract: In recent decades, the Altland-Zirnabuer (AZ) table has proven incredibly powerful in delineating constraints for topological classification of a given band-insulator based on dimension and (nonspatial) symmetry class, and has also been expanded by considering additional crystalline symmetries. Nevertheless, realizing a three-dimensional (3D), time-reversal symmetric (class AII) topological insulator (TI) in the absence of reflection symmetries, with a classification beyond the $\mathbb{Z}_{2}$ paradigm remains an open problem. In this work we present a general procedure for constructing such systems within the framework of projected topological branes (PTBs). In particular, a 3D projected brane from a "parent" four-dimensional topological insulator exhibits a $\mathbb{Z}$ topological classification, corroborated through its response to the inserted bulk monopole loop. More generally, PTBs have been demonstrated to be an effective route to performing dimensional reduction and embedding the topology of a $(d+1)$-dimensional "parent" Hamiltonian in $d$ dimensions, yielding lower-dimensional topological phases beyond the AZ classification without additional symmetries. Our findings should be relevant for the metamaterial platforms, such as photonic and phonic crystals, topolectric circuits, and designer systems.

Impact of the Fizeau drag effect on Goos-H\"{a}nchen shifts in graphene
Rafi Ud Din, Muzamil Shah, Reza Asgari, Gao Xianlong
arXiv:2312.04850v2 Announce Type: replace Abstract: We investigate the Goos-H\"{a}nchen shifts in reflection for a light beam within a graphene structure, utilizing the Fizeau drag effect induced by its massless Dirac electrons in incident light. The magnitudes of spatial and angular shifts for a light beam propagating against the direction of drifting electrons are significantly enhanced, while shifts for a beam co-propagating with the drifting electrons are suppressed. The Goos-H\"{a}nchen shifts exhibit augmentation with increasing drift velocities of electrons in graphene. The impact of incident wavelength on the angular and spatial shifts in reflection is discussed. Furthermore, the study highlights the crucial roles of the density of charged particles in graphene, the particle relaxation time, and the thickness of the graphene in manipulating the drag-affected Goos-H\"{a}nchen shifts. This investigation offers valuable insights for efficiently guiding light in graphene structures under the influence of the Fizeau drag effect.

Critical slowing of the spin and charge density wave order in thin film Cr following photoexcitation
Sheena K. K. Patel, Oleg Yu. Gorobtsov, Devin Cela, Stjepan B. Hrkac, Nelson Hua, Rajasekhar Medapalli, Anatoly G. Shabalin, James Wingert, James M. Glownia, Diling Zhu, Matthieu Chollet, Oleg G. Shpyrko, Andrej Singer, Eric E. Fullerton
arXiv:2403.00267v2 Announce Type: replace Abstract: We report on the evolution of the charge density wave (CDW) and spin density wave (SDW) order of a chromium film following photoexcitation with an ultrafast optical laser pulse. The CDW is measured by ultrafast time-resolved x-ray diffraction of the CDW satellite that tracks the suppression and recovery of the CDW following photoexcitation. We find that as the temperature of the film approaches a discontinuous phase transition in the CDW and SDW order, the time scales of recovery increase exponentially from the expected thermal time scales. We extend a Landau model for SDW systems to account for this critical slowing with the appropriate boundary conditions imposed by the geometry of the thin film system. This model allows us to assess the energy barrier between available CDW/SDW states with different spatial periodicities.

Gapped nodal planes drive a large topological Nernst effect in a chiral lattice antiferromagnet
N. D. Khanh, S. Minami, M. Hirschmann, T. Nomoto, M. C. Jiang, R. Yamada, D. Yamaguchi, Y. Hayashi, Y. Okamura, H. Watanabe, G. Y. Guo, Y. Takahashi, S. Seki, Y. Taguchi, Y. Tokura, R. Arita, M. Hirschberger
arXiv:2403.01113v2 Announce Type: replace Abstract: The electronic structure of compensated antiferromagnets (CAF) has drawn attention for its ability to create large responses, reminiscent of ferromagnets and suitable for data storage and readout, despite (nearly) net-zero spontaneous magnetization. Many of the striking experimental signatures predicted for CAF, such as giant thermoelectric Nernst effects, are enhanced when two or more electronic bands are nearly degenerate in vicinity of the Fermi energy. Here, we use thermoelectric and electric transport experiments to study the electronic structure of the layered, chiral metal CoNb3S6 in its all-in-all-out CAF ground state and report near-degeneracies of electron bands at the upper and lower boundaries of the first Brillouin zone. Considering non-symmorphic spin-space group symmetries in the non-relativistic approximation for the ordered phase, these near-degeneracies are approximately protected by a lattice translation combined with spin rotation, and are vestiges of nodal planes enforced by a screw axis symmetry in the paramagnetic state. Hot spots of emergent, or fictitious, magnetic fields are formed at the slightly gapped nodal plane, generating the spontaneous Hall and Nernst effects in this CAF. Taking into account more than six hundred Wannier orbitals, our model quantitatively reproduces the observed spontaneous Nernst effect, emphasizes the role of proximate symmetries in the emergent responses of CAF, and demonstrates the promise of ab-initio search for functional responses in a wide class of materials with reconstructed unit cells due to spin or charge order.

Exact Fractional Inference via Re-Parametrization & Interpolation between Tree-Re-Weighted- and Belief Propagation- Algorithms
Hamidreza Behjoo, Michael Chertkov
arXiv:2301.10369v2 Announce Type: replace-cross Abstract: Inference efforts -- required to compute partition function, $Z$, of an Ising model over a graph of $N$ ``spins" -- are most likely exponential in $N$. Efficient variational methods, such as Belief Propagation (BP) and Tree Re-Weighted (TRW) algorithms, compute $Z$ approximately minimizing respective (BP- or TRW-) free energy. We generalize the variational scheme building a $\lambda$-fractional-homotopy, $Z^{(\lambda)}$, where $\lambda=0$ and $\lambda=1$ correspond to TRW- and BP-approximations, respectively, and $Z^{(\lambda)}$ decreases with $\lambda$ monotonically. Moreover, this fractional scheme guarantees that in the attractive (ferromagnetic) case $Z^{(TRW)}\geq Z^{(\lambda)}\geq Z^{(BP)}$, and there exists a unique (``exact") $\lambda_*$ such that, $Z=Z^{(\lambda_*)}$. Generalizing the re-parametrization approach of \citep{wainwright_tree-based_2002} and the loop series approach of \citep{chertkov_loop_2006}, we show how to express $Z$ as a product, $\forall \lambda:\ Z=Z^{(\lambda)}{\cal Z}^{(\lambda)}$, where the multiplicative correction, ${\cal Z}^{(\lambda)}$, is an expectation over a node-independent probability distribution built from node-wise fractional marginals. Our theoretical analysis is complemented by extensive experiments with models from Ising ensembles over planar and random graphs of medium- and large- sizes. The empirical study yields a number of interesting observations, such as (a) ability to estimate ${\cal Z}^{(\lambda)}$ with $O(N^4)$ fractional samples; (b) suppression of $\lambda_*$ fluctuations with increase in $N$ for instances from a particular random Ising ensemble.

State Diagrams to determine Tree Tensor Network Operators
Richard M. Milbradt, Qunsheng Huang, Christian B. Mendl
arXiv:2311.13433v3 Announce Type: replace-cross Abstract: This work is concerned with tree tensor network operators (TTNOs) for representing quantum Hamiltonians. We first establish a mathematical framework connecting tree topologies with state diagrams. Based on these, we devise an algorithm for constructing a TTNO given a Hamiltonian. The algorithm exploits the tensor product structure of the Hamiltonian to add paths to a state diagram, while combining local operators if possible. We test the capabilities of our algorithm on random Hamiltonians for a given tree structure. Additionally, we construct explicit TTNOs for nearest neighbour interactions on a tree topology. Furthermore, we derive a bound on the bond dimension of tensor operators representing arbitrary interactions on trees. Finally, we consider an open quantum system in the form of a Heisenberg spin chain coupled to bosonic bath sites as a concrete example. We find that tree structures allow for lower bond dimensions of the Hamiltonian tensor network representation compared to a matrix product operator structure. This reduction is large enough to reduce the number of total tensor elements required as soon as the number of baths per spin reaches $3$.

On the computation of lattice sums without translational invariance
Andreas A. Buchheit, Torsten Ke{\ss}ler, Kirill Serkh
arXiv:2403.03213v2 Announce Type: replace-cross Abstract: This paper introduces a new method for the efficient computation of oscillatory multidimensional lattice sums in geometries with boundaries. Such sums are ubiquitous in both pure and applied mathematics, and have immediate applications in condensed matter physics and topological quantum physics. The challenge in their evaluation results from the combination of singular long-range interactions with the loss of translational invariance caused by the boundaries, rendering standard tools ineffective. Our work shows that these lattice sums can be generated from a generalization of the Riemann zeta function to multidimensional non-periodic lattice sums. We put forth a new representation of this zeta function together with a numerical algorithm that ensures exponential convergence across an extensive range of geometries. Notably, our method's runtime is influenced only by the complexity of the considered geometries and not by the number of particles, providing the foundation for efficient simulations of macroscopic condensed matter systems. We showcase the practical utility of our method by computing interaction energies in a three-dimensional crystal structure with $3\times 10^{23}$ particles. Our method's accuracy is demonstrated through extensive numerical experiments. A reference implementation is provided online along with this article.

Found 4 papers in prb
Date of feed: Thu, 07 Mar 2024 04:17:02 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)

Novel metallic layered dichalcogenides ${\mathrm{Pd}}_{1\text{−}x}{M}_{x}{\mathrm{Te}}_{2}$ $(M=\mathrm{Ir}, \mathrm{Rh})$ with $0≤x≤1$ in a Fermi liquid scenario
Florencia E. Lurgo, Raúl E. Carbonio, and Rodolfo D. Sánchez
Author(s): Florencia E. Lurgo, Raúl E. Carbonio, and Rodolfo D. Sánchez

The synthesis, structural analysis, and physical properties of dichalcogenide families ${\mathrm{Pd}}_{1\text{−}x}{\mathrm{Ir}}_{x}{\mathrm{Te}}_{2}$ and ${\mathrm{Pd}}_{1\text{−}x}{\mathrm{Rh}}_{x}{\mathrm{Te}}_{2}$ with $0≤x≤1$ are reported. All compositions show layered structures belonging to th…

[Phys. Rev. B 109, 094104] Published Wed Mar 06, 2024

Time-reversal invariant topological moiré flat band: A platform for the fractional quantum spin Hall effect
Yi-Ming Wu, Daniel Shaffer, Zhengzhi Wu, and Luiz H. Santos
Author(s): Yi-Ming Wu, Daniel Shaffer, Zhengzhi Wu, and Luiz H. Santos

Motivated by recent observation of the quantum spin Hall effect in monolayer germanene and twisted bilayer transition-metal dichalcogenides (TMDs), we study the topological phases of moiré twisted bilayers with time-reversal symmetry and spin ${s}_{z}$ conservation. By using a continuum model descri…

[Phys. Rev. B 109, 115111] Published Wed Mar 06, 2024

Large unconventional anomalous Hall effect arising from spin chirality within domain walls of an antiferromagnet ${\mathrm{EuZn}}_{2}{\mathrm{Sb}}_{2}$
Karan Singh, Orest Pavlosiuk, Shovan Dan, Dariusz Kaczorowski, and Piotr Wiśniewski
Author(s): Karan Singh, Orest Pavlosiuk, Shovan Dan, Dariusz Kaczorowski, and Piotr Wiśniewski

The unconventional anomalous Hall effect was observed in the antiferromagnetic state of ${\mathrm{EuZn}}_{2}{\mathrm{Sb}}_{2}$. Scaling of unconventional Hall conductivity with the longitudinal conductivity, and the magnitude of the Hall angle indicate spin chirality despite a collinear magnetic str…

[Phys. Rev. B 109, 125107] Published Wed Mar 06, 2024

Interaction-mitigated Landau damping
Xuepeng Wang, Roderich Moessner, and Debanjan Chowdhury
Author(s): Xuepeng Wang, Roderich Moessner, and Debanjan Chowdhury

Bosonic collective modes are ubiquitous in metals, but over a wide range of energy and momenta suffer from Landau damping, decaying into the continuum of particle-hole excitations. Here we point out that interactions can suppress this decay, protecting a finite fraction of the total spectral weight …

[Phys. Rev. B 109, L121102] Published Wed Mar 06, 2024

Found 3 papers in prl
Date of feed: Thu, 07 Mar 2024 04:17:01 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)

Spontaneous Stochasticity Amplifies Even Thermal Noise to the Largest Scales of Turbulence in a Few Eddy Turnover Times
Dmytro Bandak, Alexei A. Mailybaev, Gregory L. Eyink, and Nigel Goldenfeld
Author(s): Dmytro Bandak, Alexei A. Mailybaev, Gregory L. Eyink, and Nigel Goldenfeld

How predictable are turbulent flows? Here, we use theoretical estimates and shell model simulations to argue that Eulerian spontaneous stochasticity, a manifestation of the nonuniqueness of the solutions to the Euler equation that is conjectured to occur in Navier-Stokes turbulence at high Reynolds …

[Phys. Rev. Lett. 132, 104002] Published Wed Mar 06, 2024

Fractional Quantum Hall States of the $\mathcal{A}$ Phase in the Second Landau Level
Sudipto Das, Sahana Das, and Sudhansu S. Mandal
Author(s): Sudipto Das, Sahana Das, and Sudhansu S. Mandal

A proposal of the existence of an Anomalous phase ($\mathcal{A}$ phase) [Das et al., Phys. Rev. Lett. 131, 056202 (2023)] at the experimental range of moderate Landau-level-mixing strength has recently been made for the $5/2$ state. We here report that the gapped $\mathcal{A}$ phase is generic to th…

[Phys. Rev. Lett. 132, 106501] Published Wed Mar 06, 2024

Controlling Confined Collective Organization with Taxis
Albane Théry, Alexander Chamolly, and Eric Lauga
Author(s): Albane Théry, Alexander Chamolly, and Eric Lauga

Biased locomotion is a common feature of microorganisms, but little is known about its impact on self-organization. Inspired by recent experiments showing a transition to large-scale flows, we study theoretically the dynamics of magnetotactic bacteria confined to a drop. We reveal two symmetry-break…

[Phys. Rev. Lett. 132, 108301] Published Wed Mar 06, 2024

Found 4 papers in pr_res
Date of feed: Thu, 07 Mar 2024 04:17:01 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)

Strongly interacting photonic quantum walk using single atom beamsplitters
Xinyuan Zheng and Edo Waks
Author(s): Xinyuan Zheng and Edo Waks

Photonics provide an efficient way to implement quantum walks, the quantum analog of classical random walks, which demonstrate rich physics with potential applications. However, most photonic quantum walks do not involve photon interactions, which limits their potential to explore strongly correlate…

[Phys. Rev. Research 6, 013245] Published Wed Mar 06, 2024

Dynamic mass generation and topological order in overscreened Kondo lattices
Yang Ge and Yashar Komijani
Author(s): Yang Ge and Yashar Komijani

Multichannel Kondo lattice models are examples of strongly correlated electronic systems that exhibit non-Fermi-liquid behavior due to the presence of a continuous channel symmetry. Mean-field analyses have predicted that these systems undergo channel symmetry breaking at low temperature. We use the…

[Phys. Rev. Research 6, 013247] Published Wed Mar 06, 2024

Control of the Purcell effect via unexcited atoms and exceptional points
G. S. Agarwal
Author(s): G. S. Agarwal

This article shows how an unexcited atom affects the Purcell decay, depending on the coupling state.

[Phys. Rev. Research 6, L012050] Published Wed Mar 06, 2024

Gate-defined superconducting channel in magic-angle twisted bilayer graphene
Giulia Zheng, Elías Portolés, Alexandra Mestre-Torà, Marta Perego, Takashi Taniguchi, Kenji Watanabe, Peter Rickhaus, Folkert K. de Vries, Thomas Ihn, Klaus Ensslin, and Shuichi Iwakiri
Author(s): Giulia Zheng, Elías Portolés, Alexandra Mestre-Torà, Marta Perego, Takashi Taniguchi, Kenji Watanabe, Peter Rickhaus, Folkert K. de Vries, Thomas Ihn, Klaus Ensslin, and Shuichi Iwakiri

The supercurrent through a narrow channel in magic-angle twisted bilayer graphene can be turned on and off by tuning the gate-defined constriction.

[Phys. Rev. Research 6, L012051] Published Wed Mar 06, 2024

Found 1 papers in nano-lett
Date of feed: Wed, 06 Mar 2024 14:17:08 GMT

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[ASAP] Graphene Failure under MPa: Nanowear of Step Edges Initiated by Interfacial Mechanochemical Reactions
Chuan Tang, Yilong Jiang, Chao Chen, Chen Xiao, Junhui Sun, Linmao Qian, and Lei Chen

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Nano Letters
DOI: 10.1021/acs.nanolett.3c04335