Found 43 papers in cond-mat

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Statistical mechanics of elastica for the shape of supercoiled DNA: hyperelliptic elastica of genus three
Shigeki Matsutani
This article studies the statistical mechanics of elastica as a model of the shapes of the supercoiled DNA, and shows that its excited states can be characterized by the focusing modified KdV (MKdV) equation due to thermal fluctuation. Following the previous paper (Matsutani and Previato, Physica D 430 (2022) 133073), the hyperelliptic solutions of the focusing modified KdV (MKdV) equation of genus three are considered. There appears a pattern as a repetition of the modulation of figure-eight and the inverse 'S' as a thermal fluctuation of elastica, called the S-eight mode. Our model states that the excited states of elastica due to the thermal effect have the S-eight mode, which reproduces the shapes of the AFM image of the supercoiled DNAs observed by Japaridze et al. (Nano Lett. 17 3, (2017) 1938).

Generalization of the Landauer-B\"uttiker theory onto the case of dissipative contacts
Andrey R. Kolovsky
We revisit the problem of two-terminal transport of non-interacting Fermi particles in a mesoscopic device. First, we generalize the problem by including into consideration relaxation processes in contacts (which are characterized by the contact self-thermalization rate $\gamma$) and then solve it by using the master equation approach. In the limit $\gamma\rightarrow0$ the obtained results are shown to reproduce those of the Landauer-B\"uttiker theory. Thus, the presented analysis proves analytical correspondence between the Landauer-B\"uttiker and master-equation approaches to quantum transport, -- the problem which resisted solution for decades.

Exploring $\rm Mg^{2+}$ and $\rm Ca^{2+}$ Conductors Via Solid-State Metathesis Reactions
Titus Masese Godwill Mbiti Kanyolo Yoshinobu Miyazaki Shintaro Tachibana Sachio Komori Tomoyasu Taniyama Yuki Orikasa Tomohiro Saito
Magnesium and calcium batteries offer promising energy storage solutions characterised by cost-effectiveness, safety, and high energy density. However, the scarcity of viable electrode and electrolyte materials vastly hinders their advancement. This study utilises solid-state metathetical reactions involving predominantly chalcogen- and pnictogen-based honeycomb layered oxides with alkaline-earth halides/nitrates to synthesise $\rm Mg^{2+}$- and $\rm Ca^{2+}$-based materials previously achievable only under high-temperature/high-pressure conditions, as well as new metastable materials with unique crystal versatility. Particularly, we employ metathetical reactions involving $\rm Li_4MgTeO_6$, $\rm Na_2Mg_2TeO_6$, and $\rm Na_4MgTeO_6$ with $\rm MgCl_2/Mg(NO_3)_2$ or $\rm Ca(NO_3)_2$ at temperatures not exceeding 500$\,^{\circ}$C to produce $\rm Mg_3TeO_6$ polymorphs, ilmenite-type $\rm CaMg_2TeO_6$ ($\rm Mg_2CaTeO_6$), and double perovskite $\rm Ca_2MgTeO_6$. Thus, we demonstrate that these materials, conventionally requiring gigascale pressures and high temperatures ($> 1000\,^{\circ}$C) for their proper synthesis, are now readily accessible at ambient pressure and considerably lower temperatures. Meanwhile, despite sub-optimal pellet densities, the synthesised ilmenite-type $\rm Mg_3TeO_6$ and double perovskite ${\rm Ca}_2M\rm TeO_6$ ($M = \rm Mg,Ca,Zn$) materials exhibit remarkable bulk ionic conductivity at room temperature, marking them as promising compositional spaces for exploring novel $\rm Mg^{2+}$ and $\rm Ca^{2+}$ conductors. Furthermore, this study extends the applicability of metathetical reactions to attain $\rm Mg$- or $\rm Ca$-based bismuthates, antimonates, ruthenates, tungstates, titanates, phosphates, and silicates, thus opening avenues to novel multifunctional nanomaterial platforms with utility in energy storage and beyond.

Electrokinetic origin of swirling flow on nanoscale interface
Shuangshuang Meng Yu Han Wei Zhao Yueqiang Zhu Chen Zhang Xiaoqiang Feng Ce Zhang Duyang Zang Guangyin Jing Kaige Wang
The zeta ($\zeta$) potential is a pivotal metric for characterizing the electric field topology within an electric double layer - an important phenomenon on phase interface. It underpins critical processes in diverse realms such as chemistry, biomedical engineering, and micro/nanofluidics. Yet, local measurement of $\zeta$ potential at the interface has historically presented challenges, leading researchers to simplify a chemically homogenized surface with a uniform $\zeta$ potential. In the current investigation, we present evidence that, within a microchannel, the spatial distribution of $\zeta$ potential across a chemically homogeneous solid-liquid interface can become two-dimensional (2D) under an imposed flow regime, as disclosed by a state-of-art fluorescence photobleaching electrochemistry analyzer (FLEA) technique. The $\zeta$ potential' s propensity to become increasingly negative downstream, presents an approximately symmetric, V-shaped pattern in the spanwise orientation. Intriguingly, and of notable significance to chemistry and engineering, this 2D $\zeta$ potential framework was found to electrokinetically induce swirling flows in tens of nanometers, aligning with the streamwise axis, bearing a remarkable resemblance to the well-documented hairpin vortices in turbulent boundary layers. Our findings gesture towards a novel perspective on the genesis of vortex structures in nanoscale. Additionally, the FLEA technique emerges as a potent tool for discerning $\zeta$ potential at a local scale with high resolution, potentially accelerating the evolution and applications of novel surface material.

Broken Symmetry in Ideal Chern Bands
Hui Liu Kang Yang Ahmed Abouelkomsan Zhao Liu Emil J. Bergholtz
Recent observations of the fractional anomalous quantum Hall effect in moir\'e materials have reignited the interest in fractional Chern insulators (FCIs). The chiral limit in which analytic Landau level-like single-particle states form an "ideal" Chern band and local interactions lead to Laughlin-like FCIs at $1/3$ filling, has been very useful for understanding these systems by relating them to the lowest Landau level. We show, however, that, even in the idealized chiral limit, a fluctuating quantum geometry is associated with strongly broken symmetries and a phenomenology very different from that of Landau levels. In particular, particle-hole symmetry is strongly violated and e.g. at $2/3$ filling an emergent interaction driven Fermi liquid state with no Landau level counterpart is energetically favoured. In fact, even the exact Laughlin-like zero modes at $1/3$ filling have a non-uniform density tracking the underlying quantum geometry. Moreover, by switching to a Coulomb interaction, the ideal Chern band features charge density wave states with no lowest Landau level counterpart.

Probing magnetism in moir\'e heterostructures with quantum twisting microscopes
Fabian Pichler Wilhelm Kadow Clemens Kuhlenkamp Michael Knap
Spin-ordered states close to metal-insulator transitions are poorly understood theoretically and challenging to probe in experiments. Here, we propose that the quantum twisting microscope, which provides direct access to the energy-momentum resolved spectrum of single-particle and collective excitations, can be used as a novel tool to distinguish between different types of magnetic order. To this end, we calculate the single-particle spectral function and the dynamical spin-structure factor for both a ferromagnetic and antiferromagnetic generalized Wigner crystal formed in fractionally filled moir\'e superlattices of transition metal dichalcogenide heterostructures. We demonstrate that magnetic order can be clearly identified in these response functions. Furthermore, we explore signatures of quantum phase transitions in the quantum twisting microscope response. We focus on the specific case of triangular moir\'e lattices at half filling, which have been proposed to host a topological phase transition between a chiral spin liquid and a 120 degree ordered state. Our work demonstrates the potential for quantum twisting microscopes to characterize quantum magnetism in moir\'e heterostructures.

Graphene field-effect transistors for sensing ion-channel coupled receptors: towards biohybrid nanoelectronics for chemical detection
Oc\'eane Terral Guillaume Audic Arnaud Claudel Justine Magnat Aur\'elie Dupont Christophe J. Moreau C\'ecile Delacour
Graphene field effect transistors (G-FETs) have appeared as suitable candidates for sensing charges and have thus attracted large interest for ion and chemical detections. In particular, their high sensitivity, chemical robustness, transparency and bendability offer a unique combination for interfacing living and soft matters. Here we have demonstrated their ability to sense targeted biomolecules, by combining them with ion channels-coupled receptors (ICCRs). These receptors have been naturally or artificially expressed within living cell membranes to generate ion fluxes in presence of chemicals of interest. Here, we have successfully combined those biosensors with G-FET array which converts the bio-activation of the ICCRs into readable electronic signals. This hybrid bioelectronic device leverages the advantages of the biological receptor and the graphene field effect transistor enabling the selective detection of biomolecules, which is a current shortcoming of electronic sensors. Additionally, the G-FET allows to discriminate the polarity of the ion fluxes which otherwise remains hidden from conventional electrophysiological recordings. The multisite recording ability offered by the G-FET array rises numerous possibilities for multiscale sensing and high throughput screening of cellular solutions or analytes, which is of both fundamental and applied interests in health and environment monitoring.

Giant piezoelectricity in group IV monochalcogenides with ferroelectric AA layer stacking
Seungjun Lee Hyeong-Ryul Kim Wei Jiang Young-Kyun Kwon Tony Low
The piezoelectricity of group IV monochalcogenides (MXs, with M = Ge, Sn and X = S, Se) has attracted much attention due to their substantially higher piezoelectric coefficients compared to other 2D materials. However, with increasing layer number, their piezoelectricity rapidly disappears due to the antiferroelectric stacking order, severely limiting their practical applications. Using first-principles calculations, we investigated the piezoelectricity of MXs with the ferroelectric AA stacking configuration, which has recently been stabilized in experiments. We found that AA-stacked MXs have a ferroelectric ground state with the smallest lattice constant among other stacking configurations, resulting in a giant piezoelectric coefficient, which is the first demonstration of a strategy where the piezoelectric coefficients can increase with the number of layers. This can be attributed to a strong negative correlation between the lattice constant along the armchair direction and the piezoelectric coefficient, and spontaneous compressive strain stabilized in ferroelectric AA stacking configuration.

Resonant Raman scattering of surface phonon polaritons mediated by excitons in WSe$_2$ films
L. Zhou K. Wirth M. N. Bui R. Rani D. Gr\"utzmacher T. Taubner B. E. Kardyna{\l}
Surface phonon-polaritons propagating along interfaces of polar dielectrics coexist with excitons in many van der Waals heterostructures, so understanding their mutual interactions is of great interest. Here, we investigate the type I surface phonon polariton of hBN via low-temperature resonant-Raman spectroscopy in hBN/WSe2 heterostructures. The resonantly enhanced hBN surface phonon polariton (SPhP) Raman signal, when laser energy is such that the scattered photons have energy close to that of the WSe2 excitons, enables detailed characterization of type I SPhP in hBN even when hBN is one monolayer thick. We find that the measured bandwidth of the SPhP Raman signal depends on the thicknesses of the hBN layer. We are able explain the experimental data using transfer matrix method simulations of SPhP dispersions providing that we assume the Raman scattering to be momentum non-conserving, as could be the case if localized WSe2 exciton states participated in the process. We further show that resonant Raman scattering from SiO2 SPhP can also be mediated by WSe$_2$.

Probing the Polarization of Low-Energy Excitations in 2D Materials from Atomic Crystals to Nanophotonic Arrays using Momentum-Resolved Electron Energy Loss Spectroscopy
Andrew W. Rossi Marc R. Bourgeois Caleb Walton David J. Masiello
Spectroscopies utilizing free electron beams as probes offer detailed information on the reciprocal-space excitations of 2D materials such as graphene and transition metal dichalcogenide monolayers. Yet, despite the attention paid to such quantum materials, less consideration has been given to the electron-beam characterization of 2D periodic nanostructures such as photonic crystals, metasurfaces, and plasmon arrays, which can exhibit the same lattice and excitation symmetries as their atomic analogs albeit at drastically different length, momentum, and energy scales. Due to their lack of covalent bonding and influence of retarded electromagnetic interactions, important physical distinctions arise that complicate interpretation of scattering signals. Here we present a fully-retarded theoretical framework for describing the inelastic scattering of wide field electron beams from 2D materials and apply it to investigate the complementarity in sample excitation information gained in the measurement of a honeycomb plasmon array versus angle-resolved optical spectroscopy in comparison to single monolayer graphene.

Nodal fermions in a strongly spin-orbit coupled frustrated pyrochlore superconductor
Dongjin Oh Junha Kang Yuting Qian Shiang Fang Mingu Kang Chris Jozwiak Aaron Bostwick Eli Rotenberg Joseph G. Checkelsky Liang Fu Tomasz Klimczuk Michal J. Winiarski Bohm-Jung Yang Riccardo Comin
The pyrochlore lattice, a three-dimensional network of corner-sharing tetrahedra, is a promising material playground for correlated topological phases arising from the interplay between spin-orbit coupling (SOC) and electron-electron interactions. Due to its geometrically frustrated lattice structure, exotic correlated states on the pyrochlore lattice have been extensively studied using various spin Hamiltonians in the localized limit. On the other hand, the topological properties of the electronic structure in the pyrochlore lattice have rarely been explored, due to the scarcity of pyrochlore materials in the itinerant paramagnetic limit. Here, we explore the topological electronic band structure of pyrochlore superconductor RbBi$_{2}$ using angle-resolved photoemission spectroscopy. Thanks to the strong SOC of the Bi pyrochlore network, we experimentally confirm the existence of three-dimensional (3D) massless Dirac fermions enforced by nonsymmorphic symmetry, as well as a 3D quadratic band crossing protected by cubic crystalline symmetry. Furthermore, we identify an additional 3D linear Dirac dispersion associated with band inversion protected by threefold rotation symmetry. These observations reveal the rich non-trivial band topology of itinerant pyrochlore lattice systems in the strong SOC regime. Through manipulation of electron correlations and SOC of the frustrated pyrochlore lattices, this material platform is a natural host for exotic phases of matter, including the fractionalized quantum spin Hall effect in the topological Mott insulator phase, as well as axion electrodynamics in the axion insulator phase.

Persistent anomaly in dynamical quantum phase transition in long-range non-Hermitian $p$-wave Kitaev chian
Debashish Mondal Tanay Nag
Considering a non-Hermitian version of $p$-wave Kitaev chain in the presence of additional second nearest neighbour tunneling, we study dynamical quantum phase transition (DQPT) which accounts for the vanishing Loschmidt amplitude. The locus of the Fisher's zero traces a continuous path on the complex time plane for the Hermitian case while it becomes discontinuous for non-Hermitian cases. This further leads to the half-unit jumps in the winding number characterizing a dynamical topological aspect of DQPT for non-Hermitian Hamiltonian. Uncovering the interplay between non-Hermiticity and long-range tunneling, we find these features to be universally present irrespective of the additional second nearest neighbour tunneling terms as long as non-Hermiticity is preserved.

Low-lying excited states quantum entanglement and continuous quantum phase transitions: The criticality of a one-dimensional deconfined critical point
Yan-Chao Li Yuan-Hang Zhou Yuan Zhang Hai-Qing Lin
From the perspective of low-lying excited states, we study the deconfined quantum critical point (DQCP) in a one-dimensional quantum spin chain by means of the entanglement entropy and fidelity. Our results show that there is a close connection between the reconstruction of low-lying excitation spectra and the DQCP. The precise position of the critical point and its continuous nature is indicated by the singular behavior of the entanglement and fidelity of the first-excited state. Furthermore, compared with the Berezinskii-Kosterlitz-Thouless type phase transitions, which also go beyond the scope of Landau-Ginzburg-Wilson paradigm, we attempt to reveal the essence of different types of symmetries on both sides of the DQPT from different manifestations of entanglement singularity.

Momentum-resolved resonant photoelectron spectroscopic study for 1T-TiSe$_2$: Observation of negative q in the Fano resonance due to inter-atomic interaction in the valence band
Shin-ichiro Tanaka Shigemasa Suga Keiji Ueno Keisuke Fukutani Fumihiko Matsui
The remarkable properties of (1T-)TiSe$_2$ among the transition metal dichalcogenides have attracted the attention of many researchers due to its peculiar behavior during the charge density wave (CDW) transition. Therefore, it is highly desirable to study its electronic structure down to the atomic orbitals. In the present research, we applied momentum-resolved resonant photoelectron spectroscopy to study TiSe$_2$ at the Ti2p-Ti3d absorption edge by using a momentum microscope, which can simultaneously detect the electronic states in a wide $(k_x,k_y)$ range. We have also used constant initial state (CIS) spectroscopy and density functional theory (DFT) calculations to reveal the hybridization between the Ti3d and Se4p orbitals within the valence band at the Gamma point at room temperature. In addition, an interesting result comes from our analysis of the CIS spectrum for the energy band located at a binding energy of 2 eV at the M-point. This band, mainly composed of the Se4p orbital, exhibited a Fano line profile at the Ti2p edge, with a negative value of the parameter "$q$". This is the first clear evidence of the inter-atomic interaction during the valence band photoelectron emission process. This behavior differs significantly from the standard resonant photoelectron emission, which usually involves intra-atomic interactions. It also differs from the multi-atom resonant photoelectron emission (MARPE) observed in the core-level photoelectron emission, as we focus on the photoelectron emission from the valence band in this research.

Anatomy of localized edge modes in laterally coupled waveguides
Vadym Iurchuk Sven Stienen J\"urgen Lindner Attila K\'akay
We present a systematic micromagnetic study of standing spin-wave modes in infinitely long Permalloy strips with rectangular cross-section. Using a finite-element dynamic-matrix method, we first calculate the eigenfrequencies and the corresponding eigenvectors (mode profiles), as a function of the in-plane magnetic field applied across the strip. The ferromagnetic resonance spectra is computed from the mode profiles, assuming a homogeneous radio-frequency excitation, equivalently to an experimental ferromagnetic resonance measurement. The investigation of the field-dependent mode profiles enables for the classification of the observed resonances, here focusing mostly on the true edge mode localized at the vicinity of strip edges. Furthermore, we study the mode localization in pairs of 50-nm-thick Permalloy strips as a function of the strip width and their lateral separation. For closely spaced strips, the spatial profile of the quasi-uniform mode is substantially modified due to a significant hybridization with the edge-localized standing spin-wave modes of the neighbouring strip. We show that a wide-range-tunability of the localized edge-mode resonances can be achieved with a precise control of the magnetostatic coupling between the strips. Extreme sensitivity of the edge mode frequency on the bias field demonstrates a potential of the edge resonances for field sensing. Furthermore, for narrow strips (~100 nm in width), due to the reduced number of the allowed confined modes, a field-controllable switching between the resonances localized either in the strip center or at the edges of the strips can be achieved.

Phase stability and mechanical property trends for MAB phases by high-throughput ab initio calculations
Nikola Koutn\'a Lars Hultman Paul H. Mayrhofer Davide G. Sangiovanni
MAB phases (MABs) are atomically-thin laminates of ceramic/metallic-like layers, having made a breakthrough in the development of 2D materials. Though theoretically offering a vast chemical and phase space, relatively few MABs have yet been synthesised. To guide experiments, we perform a systematic high-throughput {\it{ab initio}} screening of MABs that combine group 4--7 transition metals (M); Al, Si, Ga, Ge, or In (A); and boron (B) focusing on their phase stability trends and mechanical properties. Considering the 1:1:1, 2:1:1, 2:1:2, 3:1:2, 3:1:3, and 3:1:4 M:A:B ratios and 10 phase prototypes, possible stabilisation of a single-phase compound for each elemental combination is assessed through formation energy spectra of the competing mechanically and dynamically stable MABs. Based on the volumetric proximity of energetically-close phases, we identify systems in which volume-changing deformations may facilitate transformation toughening. Subsequently, chemistry- and phase-structure-related trends in the elastic stiffness and ductility are predicted using elastic-constants-based descriptors. The analysis of directional Cauchy pressures and Young's moduli allows comparing mechanical response parallel and normal to M--B/A layers. Among the suggested most promising MABs are Nb$_3$AlB$_4$, Cr$_2$SiB$_2$, Mn$_2$SiB$_2$ or the already synthesised MoAlB.

Suppression of nucleation density in twisted graphene domains grown on graphene/SiC template by sequential thermal process
Yao Yao Taiki Inoue Makoto Takamura Yoshitaka Taniyasu Yoshihiro Kobayashi
We investigated the growth of twisted graphene on graphene/silicon carbide (SiC-G) templates by metal-free chemical vapor deposition (CVD) through a sequential thermal (ST) process, which exploits the ultraclean surface of SiC-G without exposing the surface to air before CVD. By conducting control experiments with SiC-G templates exposed to air (AirE process), structural analysis by atomic force microscopy revealed that the nucleation density of CVD graphene (CVD-G) was significantly suppressed in the ST process under the same growth condition. The nucleation behavior on SiC-G surfaces is observed to be very sensitive to carbon source concentration and process temperature. The nucleation on the ultraclean surface of SiC-G prepared by the ST process requires higher partial pressure of carbon source compared with that on the surface by the AirE process. Moreover, analysis of CVD-G growth over a wide temperature range indicates that nucleation phenomena change dramatically with a threshold temperature of 1300{\deg}C, possibly due to arising of etching effects. The successful synthesis of twisted few-layer graphene (tFLG) was affirmed by Raman spectroscopy, in which analysis of the G' band proves a high ratio of twisted structure in CVD-G. These results demonstrate that metal-free CVD utilizing ultraclean templates is an effective approach for the scalable production of large-domain tFLG that is valuable for electronic applications.

Fine-Tuning of the Excitonic Response in Monolayer WS2 Domes via Coupled Pressure and Strain Variation
Elena Stellino Beatrice D'Al\`o Elena Blundo Paolo Postorino Antonio Polimeni
We present a spectroscopic investigation into the vibrational and optoelectronic properties of WS2 domes in the 0-0.65 GPa range. The pressure evolution of the system morphology, deduced by the combined analysis of Raman and photoluminescence spectra, revealed a significant variation in the dome's aspect ratio. The modification of the dome shape caused major changes in the mechanical properties of the system resulting in a sizable increase of the out-of-plane compressive strain while keeping the in-plane tensile strain unchanged. The variation of the strain gradients drives a non-linear behavior in both the exciton energy and radiative recombination intensity, interpreted as the consequence of a hybridization mechanism between the electronic states of two distinct minima in the conduction band. Our results indicate that pressure and strain can be efficiently combined in low dimensional systems with unconventional morphology to obtain modulations of the electronic band structure not achievable in planar crystals.

Energy Dissipation to Tungsten Surfaces upon Eley-Rideal Recombination of N2 and H2
O. Galparsoro R. P\'etuya J. I. Juaristi C. Crespos M. Alducin P. Larr\'egaray
Quasiclassical molecular dynamics simulations are performed to investigate energy dissipation to the (100) and (110) tungsten surfaces upon Eley-Rideal (ER) recombination of H2 and N2. Calculations are carried out within the single adsorbate limit under normal incidence. A generalized Langevin surface oscillator (GLO) scheme is used to simulate the coupling to phonons, whereas electron-hole (e-h) pair excitations are implemented using the local density friction approximation (LDFA). Phonon excitations are found to reduce the ER reactivity for N2 recombination, but do not affect H abstraction. In contrast, the effect of e-h pair excitations on the ER recombination cross section is small for N2, but can be important for H2. The analysis of the energy lost by the recombined species shows that most of the energy is dissipated into phonon excitations in the N2 recombination and into electronic excitations in the H2 recombination. In all cases, the energy dissipated into e-h pairs is taken away from the translational kinetic energy of the formed molecules, whereas dissipation to phonons, only significant for N2, also affects vibration. Interestingly, the electron mediated energy losses are found to be smaller in the case of N2 when surface motion is allowed.

Hidden non-equilibrium pathways towards crystalline perfection
A. Mangu V. A. Stoica H. Zheng T. Yang M. Zhang H. Wang Q. L. Nguyen S. Song S. Das P. Meisenheimer E. Donoway M. Chollet Y. Sun J. J. Turner J. W. Freeland H. Wen L. W. Martin L. -Q. Chen V. Gopalan D. Zhu Y. Cao A. M. Lindenberg
A central paradigm of non-equilibrium physics concerns the dynamics of heterogeneity and disorder, impacting processes ranging from the behavior of glasses1 to the emergent functionality of active matter. Understanding these complex mesoscopic systems requires probing the microscopic trajectories associated with irreversible processes, the role of fluctuations and entropy growth, and the timescales on which non-equilibrium responses are ultimately maintained. Approaches that illuminate these processes in model systems may enable a more general understanding of other heterogeneous non-equilibrium phenomena, and potentially define ultimate speed and energy cost limits for information processing technologies. Here, we apply ultrafast single shot x-ray photon correlation spectroscopy (XPCS) to resolve the non-equilibrium, heterogeneous, and irreversible mesoscale dynamics during a light-induced phase transition. This approach defines a new way of capturing the nucleation of the induced phase, the formation of transient mesoscale defects at the boundaries of the nuclei, and the eventual disappearance of these defects, even in systems with complex polarization topologies. A non-equilibrium, sub-diffusive response spanning >10 orders of magnitude in timescales is observed with multistep behavior similar to the plateaus observed in supercooled liquids or glasses. We show how the observed time-dependent long-time correlations can be understood in terms of the stochastic dynamics of domain walls, encoded in effective waiting-time distributions with power-law tails. This work defines new possibilities for probing the non-equilibrium dynamics of disordered and heterogeneous media.

Heat transport through an open coupled scalar field theory hosting stability-to-instability transition
T. R. Vishnu Dibyendu Roy
We investigate heat transport through a one-dimensional open coupled scalar field theory, depicted as a network of harmonic oscillators connected to thermal baths at the boundaries. The non-Hermitian dynamical matrix of the network undergoes a stability-to-instability transition at the exceptional points as the coupling strength between the scalar fields increases. The open network in the unstable regime, marked by the emergence of inverted oscillator modes, does not acquire a steady state, and the heat conduction is then unbounded for general bath couplings. In this work, we engineer a unique bath coupling where a single bath is connected to two fields at each edge with the same strength. This configuration leads to a finite steady-state heat conduction in the network, even in the unstable regime. We also study general bath couplings, e.g., connecting two fields to two separate baths at each boundary, which shows an exciting signature of approaching the unstable regime for massive fields. We derive analytical expressions for high-temperature classical heat current through the network for different bath couplings at the edges and compare them. Furthermore, we determine the temperature dependence of low-temperature quantum heat current in different cases. Our study will help to probe topological phases and phase transitions in various quadratic Hermitian bosonic models whose dynamical matrices resemble non-Hermitian Hamiltonians, hosting exciting topological phases.

Observation of Giant Spin Splitting and d-wave Spin Texture in Room Temperature Altermagnet RuO2
Zihan Lin Dong Chen Wenlong Lu Xin Liang Shiyu Feng Kohei Yamagami Jacek Osiecki Mats Leandersson Balasubramanian Thiagarajan Junwei Liu Claudia Felser Junzhang Ma
Recently, a novel magnetic phase called altermagnetism has been proposed, ushering in a third distinct magnetic phase beyond ferromagnetism and antiferromagnetism. It is expected that this groundbreaking phase exhibits unique physical properties such as C-paired spin-valley locking, anomalous Hall effect, nontrivial Berry phase, and giant magnetoresistance, etc. Among all the predicted candidates, several room temperature altermagnets are suggested to host significant potential applications in the near future. Nevertheless, direct evidence about the spin pattern of the room temperature altermagnet is still unrevealed. Previous studies found that RuO2 is identified as the most promising candidate for room temperature d-wave altermagnetism, exhibiting a substantial spin splitting of up to 1.4 eV. In this study, utilizing angle-resolved photoemission spectroscopy (ARPES), we report experimental observation of the spin splitting in RuO2. Furthermore, employing spin-ARPES, we directly observed the d-wave spin pattern. Our results unequivocally show that RuO2 is a perfect d-wave altermagnet with great potential for upcoming spintronic applications.

Revealing the KH2PO4 soft-mode coupling mechanism with infrared spectroscopy under pressure
D. Santos-Cottin S. Nasrallah F. Capitani P. Simon C. C. Homes A. Akrap R. P. S. M. Lobo
We measured the far-infrared reflectivity of a KH2PO4 single crystal up to pressures of 2 GPa in the ferroelectric and paraelectric phases. We find that the nu4 vibrational mode of the PO4 tetrahedron is strongly affected by the applied pressure. At ambient pressure this phonon is destabilized by the presence of the H ions and hence shows a highly damped character, beyond the phonon propagation threshold. Applying a pressure close to 0.6 GPa makes this phonon clearly underdamped. Its behavior closely follows the soft-mode behavior observed in Raman spectroscopy. Our results solve a long standing open problem, demonstrating that the nu4 mode is the excitation mediating the coupling of the hydrogen network to the lattice modes that create the ferroelectic polarization in KH2PO4.

Realization of Wess-Zumino-Witten transitions with levels $k=6$ and $k=4$ in a frustrated spin-3 chain
Natalia Chepiga
We study dimerization transitions in a frustrated spin-3 chain with next-nearest neighbor and three-site interactions. We show that two independent coupling constants of the model are sufficient to fine-tune the system to the critical point in the Wess-Zumino-Witten SU(2)$_6$ universality class. This critical point appears as the end point of an extended SU(2)$_4$ critical line. This implies that the renormalization group flow lead to the critical theory with the largest level $k$ such that the number of relevant operators is reduced by one and the parity of the level is preserved. We also report the appearance of non-magnetic Ising transition between the topologically trivial uniform and dimerized phases. This transition takes place within the singlet sector, while magnetic gap remains open.

Fluctuation-Induced First Order Transition to Collective Motion
David Martin Gianmarco Spera Hugues Chat\'e Charlie Duclut Cesare Nardini Julien Tailleur Fr\'ed\'eric van Wijland
The nature of the transition to collective motion in assemblies of aligning self-propelled particles remains a long-standing matter of debate. In this article, we focus on dry active matter and show that weak fluctuations suffice to generically turn second-order mean-field transitions into a `discontinuous' coexistence scenario. Our theory shows how fluctuations induce a density-dependence of the polar-field mass, even when this effect is absent at mean-field level. In turn, this dependency on density triggers a feedback loop between ordering and advection that ultimately leads to an inhomogeneous transition to collective motion and the emergence of non-linear travelling `flocks'. Importantly, we show that such a fluctuation-induced first order transition is present in both metric models, in which particles align with neighbors within a finite distance, and in topological ones, in which alignment is not based on relative distances. We compute analytically the noise-induced renormalization of the polar-field mass using stochastic calculus, which we further back up by a one-loop field-theoretical analysis. Finally, we confirm our analytical predictions by numerical simulations of fluctuating hydrodynamics as well as of topological microscopic models with either $k$-nearest neighbors or Voronoi alignment.

Vortex spin liquid with neutral Fermi surface and fractional quantum spin Hall effect at odd integer filling of moir\'e Chern band
Ya-Hui Zhang
There have been many progress in realizing integer and fractional quantum anomalous Hall (QAH) phases in moir\'e systems with nearly flat Chern band. More recently there is even observation of a time reversal invariant fractional phase at filling $n=3$ in twisted MoTe$_2$ bilayer at small twist angle, indicating completely new physics beyond the conventional quantum Hall systems. While an obvious interpretation is from decoupled FQAH phases in the two valleys, the absence of similar phases at fillings such as $n=\frac{2}{3}+\frac{2}{3}$ is at odds with it and suggests physics unique to the odd integer filling $n=\frac{1}{2}+\frac{1}{2}$. In this work we start from a pair of composite Fermi liquids (CFL) with opposite chiralities in the two valleys and consider the possible proximate phase after adding the inter-valley correlation. We propose a new fractional insulator through the exciton pairing of the composite fermions. This insulating phase hosts neutral Fermi surfaces and fractional quantum spin Hall (FQSH) effect. The neutral fermion is also spinless, while there is gapless spin (locked to valley) excitation from the internal flux of an U(1) gauge field. We dub the phase as a vortex spin liquid (VSL) because it can be reached from proliferating fermionic vortex of a nearby inter-valley-coherent (IVC) insulator. The phase in the bulk is essentially a quantum spin liquid as in a Mott insulator. Because the charge gap suppresses the double occupancy from the two valleys in the same region, the VSL phase may likely be energetically better than the decoupled FQSH phase. As a spin liquid, this special FQSH candidate exists only at odd integer filling, consistent with the experiment. We also discuss the potential routes from the VSL phase to competing symmetry breaking phases. \end{abstract}

Upstreamness and downstreamness in input-output analysis from local and aggregate information
Silvia Bartolucci Fabio Caccioli Francesco Caravelli Pierpaolo Vivo
Ranking sectors and countries within global value chains is of paramount importance to estimate risks and forecast growth in large economies. However, this task is often non-trivial due to the lack of complete and accurate information on the flows of money and goods between sectors and countries, which are encoded in Input-Output (I-O) tables. In this work, we show that an accurate estimation of the role played by sectors and countries in supply chain networks can be achieved without full knowledge of the I-O tables, but only relying on local and aggregate information, e.g., the total intermediate demand per sector. Our method, based on a rank-$1$ approximation to the I-O table, shows consistently good performance in reconstructing rankings (i.e., upstreamness and downstreamness measures for countries and sectors) when tested on empirical data from the World Input-Output Database. Moreover, we connect the accuracy of our approximate framework with the spectral properties of the I-O tables, which ordinarily exhibit relatively large spectral gaps. Our approach provides a fast and analytical tractable framework to rank constituents of a complex economy without the need of matrix inversions and the knowledge of finer intersectorial details.

Hyperbolic Space Spectral Characteristics in a Network of Mechanical Linkages
Nicholas H. Patino Curtis Rasmussen Massimo Ruzzene
We investigate the dynamic properties of elastic lattices defined by tessellations of a curved hyperbolic space. The lattices are obtained by projecting nodes of a regular hyperbolic tessellation onto a flat disk and then connecting those sites with simple linkages. Numerical and experimental investigations illustrate how their vibrational spectral properties are characterized by a high density of modes that are localized at the domain boundaries. Such properties govern the propagation of waves induced by broadband inputs. This suggests the potential for applications seeking the protection of bulk media from boundary-incident perturbations. We uncover the boundary-dominated nature of an exemplary hyperbolic lattice through the evaluation and analysis of its integrated density of states and vibrational spectrum. The dynamics of the lattice are also contextualized by comparing them with those of continuous disks characterized by Euclidean and hyperbolic property distributions, which confirms that the lattice retains the boundary-dominated spectrum observed in the hyperbolic plane. We then numerically investigate the response of the lattice to transient pulses incident on the boundary and find that edge-confined wave propagation occurs. The modal and transient pulse propagation behavior of the lattice is experimentally validated in a milled aluminum sample. By leveraging hyperbolic geometry, our mechanical lattice ushers in a novel class of mechanical metamaterials with boundary-dominated wave phenomena reminiscent of topologically protected systems suitable for applications in advanced wave control.

A domain wall and chiral edge current in holographic chiral phase transitions
Shuta Ishigaki Masataka Matsumoto Ryosuke Yoshii
We investigate spatially inhomogeneous solutions in a top-down holographic model: the D3/D7 model which provides a holographic description of the chiral phase transition for a finite external magnetic field, chemical potential, and temperature. We numerically find a domain wall (or kink) solution in the three dimensional space, which incorporates between the chiral symmetry broken phase at the spatial infinity, under the homogeneous sources. Along with the inhomogeneity of the chiral condensate, the charge density is also spatially modulated. The modulated charge density and finite magnetic field lead to the chiral edge current close to the domain wall. We explore the dependences of those profiles on the chemical potential and temperature near the first and second order phase transition points. Our results indicate that the inhomogeneous solutions we found are in good agreement with those obtained by the Ginzburg--Landau theory in the vicinity of the transition points.

In-plane gate induced transition asymmetry of spin-resolved Landau levels in InAs-based quantum wells
Olivio Chiatti Johannes Boy Christian Heyn Wolfgang Hansen Saskia F. Fischer
The cross-over from quasi-two- to quasi-one-dimensional electron transport subject to transverse electric fields and perpendicular magnetic fields are studied in the diffusive to quasiballistic and zero-field to quantum Hall regime. In-plane gates and Hall-bars have been fabricated from an InGaAs/InAlAs/InAs quantum well hosting a 2DEG with carrier density of about 6.8$\times$10$^{11}$ cm$^{-2}$, mobility of 1.8$\times$10$^5$ cm$^2$/Vs and an effective mass of 0.042$m_e$ after illumination. Magnetotransport measurements at temperatures down to 50 mK and fields up to 12 T yield a high effective Land\'e-factor of |g$^*$| = 16, enabling the resolution of spin-split subbands at magnetic fields of 2.5 T. In the quantum Hall regime, electrostatic control of an effective constriction width enables steering of the reflection and transmission of edge channels, allowing a separation of fully spin-polarized edge channels at filling factors ${\nu}$ = 1 und ${\nu}$ = 2. A change in the orientation of a transverse in-plane electric field in the constriction shifts the transition between Zeeman-split quantum Hall plateaus by ${\Delta}$B $\approx$ 0.1 T and is consistent with an effective magnetic field of B$_{eff}$ $\approx$ 0.13 T by spin-dependent backscattering, indicating a change in the spin-split density of states.

Ca-dimers, solvent layering, and dominant electrochemically active species in Ca(BH$_4$)$_2$ in THF
Ana Sanz Matias Fabrice Roncoroni Siddharth Sundararaman David Prendergast
Divalent ions, such as Mg, Ca, and Zn, are being considered as competitive, safe, and earth-abundant alternatives to Li-ion electrochemistry. However, the challenge remains to match electrode and electrolyte materials that stably cycle with these new formulations, based primarily on controlling interfacial phenomena. We explore the formation of electroactive species in the electrolyte Ca(BH$_4$)$_2$ in THF through molecular dynamics simulation. Free-energy analysis indicates that this electrolyte has a majority population of neutral Ca dimers and monomers, albeit with diverse molecular conformations as revealed by unsupervised learning techniques, but with an order of magnitude lower concentration of possibly electroactive charged species, such as the monocation, CaBH$_4^+$ , which we show is produced via disproportionation of neutral Ca(BH$_4$)$_2$ complexes. Dense layering of THF molecules within 1 nm of the electrode surface (modeled here using graphite) hinders the approach of reducible species to within 0.6 nm and instead enhances the local concetration of species in a narrow intermediate-density layer from 0.7-0.9 nm. A dramatic increase in the monocation population in this intermediate layer is induced at negative bias, supplied by local dimer disproportionation. We see no evidence to support any functional role of fully-solvated Ca$^{2+}$ in the electrochemical activity of this electrolyte. The consequences for performance and alternative formulations are discussed in light of this molecular-scale insight.

DFT2kp: effective kp models from ab-initio data
Jo\~ao Victor V. Cassiano Augusto L. Ara\'ujo Paulo E. Faria Junior Gerson J. Ferreira
The $\mathbf{k}\cdot\mathbf{p}$ method, combined with group theory, is an efficient approach to obtain the low energy effective Hamiltonians of crystalline materials. Although the Hamiltonian coefficients are written as matrix elements of the generalized momentum operator $\mathbf{\pi}=\mathbf{p}+\mathbf{p}_{{\rm SOC}}$ (including spin-orbit coupling corrections), their numerical values must be determined from outside sources, such as experiments or ab initio methods. Here, we develop a code to explicitly calculate the Kane (linear in crystal momentum) and Luttinger (quadratic in crystal momentum) parameters of $\mathbf{k}\cdot\mathbf{p}$ effective Hamiltonians directly from ab initio wavefunctions provided by Quantum ESPRESSO. Additionally, the code analyzes the symmetry transformations of the wavefunctions to optimize the final Hamiltonian. This is an optional step in the code, where it numerically finds the unitary transformation $U$ that rotates the basis towards an optimal symmetry-adapted representation informed by the user. Throughout the paper, we present the methodology in detail and illustrate the capabilities of the code applying it to a selection of relevant materials. Particularly, we show a "hands-on" example of how to run the code for graphene (with and without spin-orbit coupling). The code is open source and available at

Linear displacement current solely driven by the quantum metric
Longjun Xiang Bin Wang Yadong Wei Zhenhua Qiao Jian Wang
Quantum metric and Berry curvature are the real part and imaginary part of the quantum geometric tensor, respectively. The T-odd (T: time-reversal) nonlinear Hall effect driven by the quantum metric dipole, recently confirmed in Science 381, 181 (2023) and Nature 621, 487 (2023), established the geometric duality to the T-even nonlinear Hall effect that driven by the Berry curvature dipole. Interestingly, a similar geometric duality between the quantum metric and the Berry curvature, particularly for the linear response of Bloch electrons, has not been established, although the T-odd linear intrinsic anomalous Hall effect (IAHE) solely driven by the Berry curvature has been known for a long time. Herein, we develop the quantum theory for displacement current under an AC electric field. Particularly, we show that the T-even component of the linear displacement current conductivity (LDCC) is solely determined by the quantum metric, by both the response theory and the semiclassical theory. Notably, with symmetry analysis we find that the T-even LDCC can contribute a Hall current in T-invariant systems but with low symmetry, while its longitudinal component is immune to symmetry. Furthermore, employing the Dirac Hamiltonian, we arrive at a $1/\mu$ ($\mu$: chemical potential) experimental observable enhancement of the displacement current owing to the divergent behavior of quantum metric near Dirac point, similar to the IAHE at Weyl point. Our work reveals the band geometric origin of the linear displacement current and establishes, together with the IAHE, the geometric duality for the linear response of Bloch electrons. Additionally, our work offers the very first intrinsic Hall effect in T-invariant materials, which can not be envisioned in DC transport in both linear and nonlinear regimes.

Diverse universality classes of the topological deconfinement transitions of three-dimensional noncompact lattice Abelian-Higgs models
Claudio Bonati Andrea Pelissetto Ettore Vicari
We study the topological phase transitions occurring in three-dimensional (3D) multicomponent lattice Abelian-Higgs (LAH) models, in which an $N$-component scalar field is minimally coupled with a noncompact Abelian gauge field, with a global SU($N$) symmetry. Their phase diagram presents a high-temperature Coulomb (C) phase, and two low-temperature molecular (M) and Higgs (H) phases, both characterized by the spontaneous breaking of the SU($N$) symmetry. The molecular-Higgs (MH) and Coulomb-Higgs (CH) transitions are topological transitions, separating a phase with gapless gauge modes and confined charges from a phase with gapped gauge modes and deconfined charged excitations. These transitions are not described by effective Landau-Ginzburg-Wilson theories, due to the active role of the gauge modes. We show that the MH and CH transitions belong to different charged universality classes. The CH transitions are associated with the $N$-dependent charged fixed point of the renormalization-group (RG) flow of the 3D Abelian-Higgs field theory (AHFT). On the other hand, the universality class of the MH transitions is independent of $N$ and coincides with that controlling the continuous transitions of the one-component ($N=1$) LAH model. In particular, we verify that the gauge critical behavior always corresponds to that observed in the 3D inverted XY model, and that the correlations of an extended charged gauge-invariant operator (in the Lorenz gauge, this operator corresponds to the scalar field, thus it is local, justifing the use of the RG framework) have an $N$-independent critical universal behavior. This scenario is supported by numerical results for $N=1,\,2,\,25$. The MH critical behavior does not apparently have an interpretation in terms of the RG flow of the AHFT, as determined perturbatively close to four dimensions or with standard large-$N$ methods.

Anisotropic magnetism and band evolution induced by ferromagnetic phase transition in titanium-based kagome ferromagnet SmTi3Bi4
Zhe Zheng Long Chen Xuecong Ji Ying Zhou Gexing Qu Mingzhe Hu Yaobo Huang Hongming Weng Tian Qian Gang Wang
Kagome magnets with diverse topological quantum responses are crucial for next-generation topological engineering. The anisotropic magnetism and band evolution induced by ferromagnetic phase transition (FMPT) is reported in a newly discovered titanium-based kagome ferromagnet S mTi3 Bi4, which features a distorted Ti kagome lattice and S m atomic zig-zag chains. Temperature-dependent resistivity, heat capacity, and magnetic susceptibility reveal a ferromagnetic ordering temperature Tc of 23.2 K. A large magnetic anisotropy, observed by applying the magnetic field along three crystallographic axes, identifies the b axis as the easy axis. Angle-resolved photoemission spectroscopy with first-principles calculations unveils the characteristic kagome motif, including the Dirac point at the Fermi level and multiple van Hove singularities. Notably, a band splitting and gap closing attributed to FMPT is observed, originating from the exchange coupling between S m 4 f local moments and itinerant electrons of the kagome Ti atoms, as well as the time-reversal symmetry breaking induced by the long-range ferromagnetic order. Considering the large in-plane magnetization and the evolution of electronic structure under the influence of ferromagnetic ordering, such materials promise to be a new platform for exploring the intricate electronic properties and magnetic phases based on the kagome lattice.

Impact of Co2C Nanoparticles on Enhancing the Critical Current Density of Bi-2223 Superconductor
Md. Arif Ali Sourav M Karan Nirmal Roy S. S. Banerjee
We have investigated the superconducting properties of nanocomposite pellets made from Bi-2223 and Co2C powders. There is loss of superconducting fraction in the nanocomposites, but the retained superconducting fraction exhibits robust bulk superconducting properties, having Tc ~ 109 K which was found to be comparable to that of the pure Bi-2223 pellet. We found that the composites net magnetization response is a superposition of ferromagnetic and superconducting fractions contributions. We also found the surviving superconducting fraction exhibits a robust Meissner response. In the nanocomposite the irreversibility field of the superconducting fraction at 77 K is found to increase by almost three times compared to the pristine material, thereby showing strong vortex pinning features. We also find a broadened magnetic field regime over which we observe a single vortex pinning regime sustained in the nanocomposite. The critical current density, Jc, of the nanocomposite was found to be approximately five times higher than that of the pristine Bi-2223 pellet at low T. In fact, the enhancement in Jc is most significant in the high T regime, where at temperatures close to Tc in the nanocomposite we see almost two orders of magnitude increase of Jc compared to the pristine Bi-2223 pellet. The larger sized agglomeration of magnetic nanoparticles of Co2C leads to loss of superconductivity in the nanocomposite. However, there are also unagglomerated Co2C nanoparticles distributed uniformly throughout the nanocomposite which acts as efficient pinning centres allowing for collective vortex pinning centres to be retained, even upto temperatures near Tc, and these nanoparticles also do not compromise the bulk Tc of the superconducting fraction. Our study shows that these nanocomposites exhibit enhanced Jc especially in the high T regime are potentially useful for high current applications.

Energy spectra and fluxes of turbulent rotating Bose-Einstein condensates in two dimensions
Anirudh Sivakumar Pankaj Kumar Mishra Ahmad A. Hujeirat Paulsamy Muruganandam
We investigate the scaling of the energy cascade in a harmonically trapped, turbulent, rotating Bose-Einstein condensate (BEC) in two dimensions. We achieve turbulence by injecting a localized perturbation into the condensate and gradually increasing its rotation frequency from an initial value to a maximum. The main characteristics of the resulting turbulent state depend on the initial conditions, rotation frequency, and ramp-up time. We analyze the energy and the fluxes of kinetic energy by considering initial profiles without vortices and with vortex lattices. In the case without initial vortices, we find the presence of Kolmogorov-like scaling ($k^{-5/3}$) of the incompressible kinetic energy in the inertial range. However, with initial vortex lattices, the energy spectrum follows Vinen scaling ($k^{-1}$) at transient iterations. For cases with high rotating frequencies, Kolmogorov-like scaling emerges at longer durations. We observe positive kinetic energy fluxes with both initial states across all final frequencies, indicating a forward cascade of incompressible and compressible kinetic energy.

Theory of Electron Spin Resonance Spectroscopy in Scanning Tunneling Microscope
Lyuzhou Ye Xiao Zheng Xin Xu
The integration of scanning tunneling microscopy (STM) and electron spin resonance (ESR) spectroscopy has emerged as a powerful and innovative tool for discerning spin excitations and spin-spin interactions within atoms and molecules adsorbed on surfaces. However, the origin of the STM-ESR signal and the underlying mechanisms that govern the essential features of the measured spectra have remained elusive, thereby significantly impeding the future development of the STM-ESR approach. Here, we construct a model to carry out precise numerical simulations of STM-ESR spectra for a single hydrogenated Ti adatom and a hydrogenated Ti dimer, achieving excellent agreement with experimental observations. We further develop an analytic theory that elucidates the fundamental origin of the signal as well as the essential features in the measured spectra. These new theoretical developments establish a solid foundation for the on-demand detection and manipulation of atomic-scale spin states, with promising implications for cutting-edge applications in spin sensing, quantum information, and quantum computing.

Alternate cleavage structure and electronic inhomogeneity in Ca-doped YBa$_2$Cu$_3$O$_{7-\delta}$
Larissa B. Little Jennifer Coulter Ruizhe Kang Ilija Zeljkovic Dennis Huang Can-Li Song Toshinao Loew Han-Jong Chia Jason D. Hoffman John T. Markert Bernhard Keimer Boris Kozinsky Jennifer E. Hoffman
YBa$_2$Cu$_3$O$_{7-\delta}$ (YBCO) has favorable macroscopic superconducting properties of $T_\mathrm{c}$ up to 93 K and $H_{c2}$ up to 150 T. However, its nanoscale electronic structure remains mysterious because bulk-like electronic properties are not preserved near the surface of cleaved samples for easy access by local or surface-sensitive probes. It has been hypothesized that Ca-doping at the Y site could induce an alternate cleavage plane that mitigates this issue. We use scanning tunneling microscopy (STM) to study both Ca-free and 10% Ca-doped YBCO, and find that the Ca-doped samples do indeed cleave on an alternate plane, yielding a spatially-disordered partial (Y,Ca) layer. Our density functional theory calculations support the increased likelihood of this new cleavage plane in Ca-doped YBCO. On this surface, we image a superconducting gap with average value 24 $\pm$ 3 meV and characteristic length scale 1-2 nm, similar to Bi-based high-$T_\mathrm{c}$ cuprates, but the first map of gap inhomogeneity in the YBCO family.

Probing holographic flat bands at finite density
Nicol\'as Grandi Vladimir Juri\v{c}i\'c Ignacio Salazar Landea Rodrigo Soto-Garrido
Flat band electronic systems exhibit a rich landscape of correlation-driven phases. Motivated by these developments, in this paper, we explicitly include the effects of the chemical potential in a holographic model featuring approximately flat bands. In particular, we explore the phase diagram of this holographic flat band system as a function of the chemical potential. We find that at low temperatures and densities, the system features a nematic phase, transitioning into the Lifshitz phase as the chemical potential or temperature increases. To further characterize the ensuing phases, we investigate the optical conductivity and find that this observable shows strong anisotropies in the nematic phase.

Breaking of a floating particle raft by water waves
Louis Saddier Ambre Palotai Matheo Aksil Michel Tsamados Michael Berhanu
When particles of a few tens of microns are spread on the surface of water, they aggregate under the action of capillary forces and form a thin floating membrane, a particle raft. In a tank with a raft made of graphite powder, we generate in the laboratory gravity surface waves, whose wavelength {about 17 cm} is very large compared to the thickness of the raft {of order 10 microns}. For a sufficiently strong wave amplitude, the raft breaks up progressively by developing cracks and producing fragments whose sizes decrease on a time scale long compared to the period of the wave. We characterize the breaking mechanisms. Then, we investigate the area distribution of the fragments produced during the fragmentation process. The visual appearance of the fragments distributed in size and surrounded by open water bears a {notable} resemblance to the floes produced by the fracturing of sea ice by waves in the polar oceans. Fragmentation concepts and morphological tools built for sea ice floes can be applied to our macroscopic analog, on which the entire dynamic evolution is accessible. {However, the mechanic of the two systems differ, as our particle raft breaks due to the viscous stresses, whereas the sea-ice fractures due its bending by the waves.

Unveiling the hidden reaction kinetic network of carbon in water with unsupervised machine learning
Chu Li Yuan Yao Ding Pan
The dissolution of CO$_2$ in water followed by the subsequent hydrolysis reactions is of great importance to the global carbon cycle, and carbon capture and storage. Despite enormous previous studies, the reaction pathways are still not fully understood at the atomistic scale. Here, we combined \textit{ab initio} molecular dynamics simulations with Markov state models to elucidate the reaction mechanisms and kinetics of CO$_2$ in supercritical water both in the bulk and nanoconfined states. The integration of unsupervised machine learning with first-principles data allows us to automatically identify complex reaction coordinates and pathways instead of \textit{a priori} human speculation. The pyrocarbonate anion (C$_2$O$_5^{2-}$(aq)) was previously hypothesized to have a fleeting existence in water; however our study reveals that it is a crucial reaction intermediate in the nanoconfined solutions. We found that the extreme confinement can enhance the stability of C$_2$O$_5^{2-}$(aq) and even the pyrocarbonic acid (H$_2$C$_2$O$_5$(aq)), which was unknown in water. The unexpected appearance of pyrocarbonates is related to the superionic behavior of the confined solutions. Our study highlights the importance of large oxocarbons in aqueous carbon reactions, with great implications for the deep carbon cycle and the sequestration of CO$_2$.

Axion-like Quasiparticles and Topological States of Matter: Finite Density Corrections of the Chiral Anomaly Vertex
Claudio Corian\`o Mario Cret\`i Stefano Lionetti Riccardo Tommasi
We investigate the general structure of the chiral anomaly $AVV/AAA$ and $(LLL, RRR)$ vertices, in the presence of chemical potentials in perturbation theory. The study finds application in anomalous transport, whenever chirally unbalanced matter is present, with propagating external currents that are classically conserved. Examples are topological materials and the chiral magnetic effect in the plasma state of matter of the early universe. We classify the minimal number of form factors of the $AVV$ parameterization, by a complete analysis of the Schouten identities in the presence of a heat bath. We show that the longitudinal (anomaly) sector in the axial-vector channel, for on-shell and off-shell photons, is protected against corrections coming from the insertion of a chemical potential in the fermion loop. When the photons are on-shell, we prove that also the transverse sector, in the same channel, is $\mu$-independent and vanishes. The related effective action is shown to be always described by the exchange of a massless anomaly pole, as in the case of vanishing chemical potentials. The pole is interpreted as an interpolating axion-like quasiparticle generated by the anomaly. In each axial-vector channel, it is predicted to be a correlated fermion/antifermion pseudoscalar (axion-like) quasiparticle appearing in the response function, once the material is subjected to an external chiral perturbation. The cancellation of the $\mu$ dependence extends to any chiral current within the Standard Model, including examples like $B$ (baryon), $L$ (lepton), and $B-L$. This holds true irrespective of whether these currents exhibit anomalies.

Found 3 papers in prb
Date of feed: Thu, 08 Feb 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)

Hall coefficient and resistivity in the doped bilayer Hubbard model
Yin Shi, Jonathan Schirmer, and Long-Qing Chen
Author(s): Yin Shi, Jonathan Schirmer, and Long-Qing Chen

Finding and understanding non-Fermi-liquid transport behaviors are at the core of condensed matter physics. Most of the existing studies in this field were devoted to the monolayer Hubbard model, which is the minimal model that captures the essential features of high-temperature superconductivity. H…

[Phys. Rev. B 109, 075114] Published Wed Feb 07, 2024

Hidden higher-order topology in nonsymmorphic group IV and V tetragonal monolayers
Yang Xue, Wei Xu, Bao Zhao, and Zhongqin Yang
Author(s): Yang Xue, Wei Xu, Bao Zhao, and Zhongqin Yang

In recent years, two-dimensional (2D) second-order topological insulators (SOTIs) have garnered significant interest, with indications of their potential realization in various symmorphic 2D electronic materials. However, up to this point, no nonsymmorphic 2D electronic SOTIs have been identified, p…

[Phys. Rev. B 109, 075115] Published Wed Feb 07, 2024

Multipole higher-order topological semimetals
Yajuan Qi, Zhaojian He, Ke Deng, Jing Li, and Yuhua Wang
Author(s): Yajuan Qi, Zhaojian He, Ke Deng, Jing Li, and Yuhua Wang

Higher-order topological phases of matter, including insulators and semimetals, have attracted much attention, since they can induce novel multidimensional topological boundary states. Recently, a two-dimensional (2D) multipole chiral-symmetric higher-order topological insulator (MCTI) with multipol…

[Phys. Rev. B 109, L060101] Published Wed Feb 07, 2024

Found 4 papers in prl
Date of feed: Thu, 08 Feb 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)

Spontaneous Hopf Fibration in the Two-Higgs-Doublet Model
R. A. Battye and S. J. Cotterill
Author(s): R. A. Battye and S. J. Cotterill

We show that energetic considerations enforce a Hopf fibration of the standard model topology within the 2HDM whose potential has either an SO(3) or U(1) Higgs-family symmetry. This can lead to monopole and vortex solutions. We find these solutions, characterize their basic properties and demonstrat…

[Phys. Rev. Lett. 132, 061601] Published Wed Feb 07, 2024

Nondissipative Martensitic Phase Transformation after Multimillion Superelastic Cycles
Mostafa Karami, Zeyuan Zhu, Ka Hung Chan, Peng Hua, Nobumichi Tamura, and Xian Chen
Author(s): Mostafa Karami, Zeyuan Zhu, Ka Hung Chan, Peng Hua, Nobumichi Tamura, and Xian Chen

Superelastic alloys used for stents, biomedical implants, and solid-state cooling devices rely on their reversible stress-induced martensitic transformations. These applications require the alloy to sustain high deformability over millions of cycles without failure. Here, we report an alloy capable …

[Phys. Rev. Lett. 132, 066101] Published Wed Feb 07, 2024

Predicting Phase Stability at Interfaces
J. Pitfield, N. T. Taylor, and S. P. Hepplestone
Author(s): J. Pitfield, N. T. Taylor, and S. P. Hepplestone

We present the RAFFLE methodology for structural prediction of the interface between two materials and demonstrate its effectiveness by applying it to MgO encapsulated by two layers of graphene. To address the challenge of interface structure prediction, our methodology combines physical insights de…

[Phys. Rev. Lett. 132, 066201] Published Wed Feb 07, 2024

Tomasch Oscillations as Above-Gap Signature of Topological Superconductivity
Antonio Štrkalj, Xi-Rong Chen, Wei Chen, D. Y. Xing, and Oded Zilberberg
Author(s): Antonio Štrkalj, Xi-Rong Chen, Wei Chen, D. Y. Xing, and Oded Zilberberg

The identification of topological superconductors usually involves searching for in-gap modes that are protected by topology. However, in current experimental settings, the smoking-gun evidence of these in-gap modes is still lacking. In this Letter, we propose to support the distinction between two-…

[Phys. Rev. Lett. 132, 066301] Published Wed Feb 07, 2024

Found 1 papers in prx
Date of feed: Thu, 08 Feb 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)

Active Matter under Control: Insights from Response Theory
Luke K. Davis, Karel Proesmans, and Étienne Fodor
Author(s): Luke K. Davis, Karel Proesmans, and Étienne Fodor

A theoretical study finds that the most energy-efficient way to control an active-matter system is to drive it at finite speed—unlike passive-matter systems.

[Phys. Rev. X 14, 011012] Published Wed Feb 07, 2024

Found 2 papers in pr_res
Date of feed: Thu, 08 Feb 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)

Manipulating spectral topology and exceptional points by nonlinearity in non-Hermitian polariton systems
Jan Wingenbach, Stefan Schumacher, and Xuekai Ma
Author(s): Jan Wingenbach, Stefan Schumacher, and Xuekai Ma

Exceptional points (EPs), with their intriguing spectral topology, have attracted considerable attention in a broad range of physical systems, with potential sensing applications driving much of the present research in this field. Here, we investigate spectral topology and EPs in systems with signif…

[Phys. Rev. Research 6, 013148] Published Wed Feb 07, 2024

Spin squeezing with itinerant dipoles: A case for shallow lattices
David Wellnitz, Mikhail Mamaev, Thomas Bilitewski, and Ana Maria Rey
Author(s): David Wellnitz, Mikhail Mamaev, Thomas Bilitewski, and Ana Maria Rey

The generation of spin squeezing with itinerant ultracold dipoles in optical lattices is studied. Under a variety of experimentally accessible conditions, tunneling of the dipoles in the lattice is shown to protect collective correlations and enhance spin squeezing.

[Phys. Rev. Research 6, L012025] Published Wed Feb 07, 2024

Found 3 papers in nano-lett
Date of feed: Wed, 07 Feb 2024 14:06:48 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] Symmetry Breaking and Spin–Orbit Coupling for Individual Vacancy-Induced In-Gap States in MoS2 Monolayers
Thasneem Aliyar, Hongyang Ma, Radha Krishnan, Gagandeep Singh, Bi Qi Chong, Yitao Wang, Ivan Verzhbitskiy, Calvin Pei Yu Wong, Kuan Eng Johnson Goh, Ze Xiang Shen, Teck Seng Koh, Rajib Rahman, and Bent Weber

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Nano Letters
DOI: 10.1021/acs.nanolett.3c03681

[ASAP] Strain-Induced Topological Phase Transitions Covering the [math] Indicator in Orthorhombic Li2AuBi
Tan Zhang, Frank Coen, and Andrew M. Rappe

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Nano Letters
DOI: 10.1021/acs.nanolett.3c04279

[ASAP] Polarization-Dependent Memory and Erasure in Quantum Dots/Graphene Synaptic Devices
Ki-Jeong Lee, Jin Hyung Kim, Sooin Jeon, Chi Won Shin, Ha-Reem Kim, Hong-Gyu Park, and Jungkil Kim

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Nano Letters
DOI: 10.1021/acs.nanolett.4c00124

Found 1 papers in acs-nano
Date of feed: Wed, 07 Feb 2024 14:03:34 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] Tuning Pore Size in Graphene in the Angstrom Regime for Highly Selective Ion–Ion Separation
Kangning Zhao, Wan-Chi Lee, Mojtaba Rezaei, Heng-Yu Chi, Shaoxian Li, Luis Francisco Villalobos, Kuang-Jung Hsu, Yuyang Zhang, Feng-Chao Wang, and Kumar Varoon Agrawal

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ACS Nano
DOI: 10.1021/acsnano.3c11068

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)

Non-Abelian Floquet braiding and anomalous Dirac string phase in periodically driven systems
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