Found 46 papers in cond-mat

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Dissipative frequency converter: from Lindblad dynamics to non-Hermitian topology
Florian Koch, Jan Carl Budich
arXiv:2403.07991v1 Announce Type: new Abstract: A topological frequency converter represents a dynamical counterpart of the integer quantum Hall effect, where a two-level system enacts a quantized time-averaged power transfer between two driving modes of incommensurate frequency. Here, we investigate as to what extent temporal coherence in the quantum dynamics of the two-level system is important for the topological quantization of the converter. To this end, we consider dissipative channels corresponding to spontaneous decay and dephasing in the instantaneous eigenbasis of the Hamiltonian as well as spontaneous decay in a fixed basis. The dissipation is modelled using both a full Lindblad and an effective non-Hermitian (NH) Hamiltonian description. For all three dissipation channels we find a transition from the unperturbed dynamics to a quantum watchdog effect, which destroys any power transfer in the strong coupling limit. This is striking because the watchdog effect leads to perfectly adiabatic dynamics in the instantaneous eigenbasis, at first glance similar to the unperturbed case. Furthermore, it is found that dephasing immediately leads to an exponential decay of the power transfer in time due to loss of polarisation in the mixed quantum state. Finally, we discuss the appearance in the effective NH trajectory description of non-adiabatic processes, which are suppressed in the full Lindblad dynamics.

Anomalous Shiba spectrum and superconductivity induced magnetic interactions in materials with topological band inversion
Didier Ndengeyintwali, Shiva Heidari, Cody Youmans, Pavan Hosur, Pouyan Ghaemi
arXiv:2403.08028v1 Announce Type: new Abstract: We study the Shiba states in materials with bulk band inversion such as iron-based topological superconductors or doped topological insulators. We show that the structure of the Shiba state spectrum depends on the doping level relative to the chemical potential at which the band-inversion occurs. Moreover, we demonstrate that the transition from ferro-magnetic to antiferromagnetic coupling and vice versa, which is caused by the coupling of magnetic impurities through the overlap of Shiba states, is highly dependent on the doping level. Additionally, topological edge states may have a substantial impact on the Shiba states, leading to a decrease in Shiba state energies and the creation of new states when the magnetic impurity approaches the boundary.

Ultra-long relaxation of a Kramers qubit formed in a bilayer graphene quantum dot
Artem O. Denisov, Veronika Reckova, Solenn Cances, Max J. Ruckriegel, Michele Masseroni, Christoph Adam, Chuyao Tong, Jonas D. Gerber, Wei Wister Huang, Kenji Watanabe, Takashi Taniguchi, Thomas Ihn, Klaus Ensslin, Hadrien Duprez
arXiv:2403.08143v1 Announce Type: new Abstract: The intrinsic valley degree of freedom makes bilayer graphene a unique platform for emerging types of semiconducting qubits. The single-carrier quantum dot ground state exhibits a two-fold degeneracy where the two states have opposite spin and valley quantum numbers. By breaking the time-reversal symmetry of this ground state with an out-of-plane magnetic field, a novel type of qubit (Kramers qubit), encoded in the two-dimensional spin-valley subspace, becomes accessible. The Kramers qubit is robust against known spin- and valley-mixing mechanisms, as it requires a simultaneous change of both quantum numbers, potentially resulting in long relaxation and coherence times. We measure the relaxation time of a single carrier in the excited states of a bilayer graphene quantum dot at small ($\sim \mathrm{mT}$) and zero magnetic fields. We demonstrate ultra-long spin-valley relaxation times of the Kramers qubit exceeding $30~\mathrm{s}$, which is about two orders of magnitude longer than the spin relaxation time of $400~\mathrm{ms}$. The demonstrated high-fidelity single-shot readout and long relaxation times are the foundation for novel, long-lived semiconductor qubits.

Thermal Hall effect in a van der Waals ferromagnet CrI3
Chunqiang Xu, Heda Zhang, Caitlin Carnahan, Pengpeng Zhang, Di Xiao, Xianglin Ke
arXiv:2403.08180v1 Announce Type: new Abstract: CrI3 is a prototypical van der Waals ferromagnet with a magnetic honeycomb lattice. Previous inelastic neutron scattering studies have suggested topological nature of its magnetic excitations with a magnon gap at the Dirac points, which are anticipated to give rise to magnon thermal Hall effect. Here we report thermal transport properties of CrI3 and show that the long-sought thermal Hall signal anticipated for topological magnons is fairly small. In contrast, we find that CrI3 exhibits an appreciable anomalous thermal Hall signal at lower temperature which may arise from magnon-phonon hybridization or magnon-phonon scattering. These findings are anticipated to stimulate further neutron scattering studies on CrI3 single crystal, which can shed light not only on the intrinsic nature of magnetic excitations but also on the magnon-phonon interaction.

Unique electronic and optical properties of stacking-modulated bilayer graphene under external magnetic fields
Chiun-Yan Lin, Da-We Weng, Chih-Wei Chiu, Godfrey Gumbs
arXiv:2403.08274v1 Announce Type: new Abstract: This study delves into the magneto-electronic and magneto-optical properties of stacking-modulated bilayer graphene. By manipulating domain walls (DWs) across AB-BA domains periodically, we unveil oscillatory Landau subbands and the associated optical excitations. The DWs act as periodic potentials, yielding fascinating 1D spectral features. Our exploration reveals 1D phenomena localized to Bernal stacking, DW regions, and stacking boundaries, highlighting the intriguing formation of Landau state quantization influenced by the commensuration between the magnetic length and the system. The stable quantized localization within different regions leads to the emergence of unconventional quantized subbands. This study provides valuable insights into the essential properties of stacking-modulated bilayer graphene.

Sub-100-fs formation of dark excitons in monolayer WS$_2$
Pavel V. Kolesnichenko, Lukas Wittenbecher, Qianhui Zhang, Run Yan Teh, Chandni Babu, Michael S. Fuhrer, Anders Mikkelsen, Donatas Zigmantas
arXiv:2403.08390v1 Announce Type: new Abstract: Two-dimensional semiconductors based on transition metal dichalcogenides are promising for electronics and optoelectronics applications owing to their properties governed by strongly-bound bright and dark excitons. Momentum-forbidden dark excitons have recently received attention as better alternatives to bright excitons for long-range transport. However, accessing the dynamics of dark excitons is challenging experimentally. The most direct, but very complicated, experiment is transient angle-resolved photoemission electron spectroscopy: sub-100-fs formation of K-$\Lambda$-excitons in monolayer WS$_2$ has been identified previously taking advantage of momentum resolution of detected signals [1]. Here, we use a simpler setting of transient photoemission electron microscopy (with spatial resolution of 75 nm), which is inherently sensitive to dark K-$\Lambda$ excitons in monolayers of transition metal dichalcogenide and has exceptionally high temporal resolution of 13 fs. We are able to directly observe intervalley scattering (dark-exciton formation) in monolayer WS$_2$ with scattering rates in the range of 14-50 fs followed by picosecond-scale dynamics mediated by defects.

Topology of Discrete Quantum Feedback Control
Masaya Nakagawa, Masahito Ueda
arXiv:2403.08406v1 Announce Type: new Abstract: A general framework for analyzing topology of quantum channels of single-particle systems is developed to find a class of genuinely dynamical topological phases that can be realized by means of discrete quantum feedback control. We provide a symmetry classification of quantum channels by identifying ten symmetry classes of discrete quantum feedback control with projective measurements. We construct various types of topological feedback control by using topological Maxwell's demons that achieve robust feedback-controlled chiral or helical transport against noise and decoherence. Topological feedback control thus offers a versatile tool for creating and controlling nonequilibrium topological phases in open quantum systems that are distinct from non-Hermitian and Lindbladian systems and should provide a guiding principle for topology-based design of quantum feedback control.

Layered Kagome Compound Na$_2$Ni$_3$S$_4$ with Topological Flat Band
Junyao Ye, Yihao Lin, Haozhe Wang, Zida Song, Ji Feng, Weiwei Xie, Shuang Jia
arXiv:2403.08456v1 Announce Type: new Abstract: We report structural and electronic properties of Na$_2$Ni$_3$S$_4$, a quasi-two-dimensional compound composed of alternating layers of [Ni$_3$S$_4$]$^{2-}$ and Na$^{+}$. The compound features a remarkable Ni-based kagome lattice with a square planar configuration of four surrounding S atoms for each Ni atom. Magnetization and electrical measurements reveal a weak paramagnetic insulator with a gap of about 0.5 eV. Our band structure calculation highlights a set of topological flat bands of the kagome lattice derived from the rotated d$_{xz}$-orbital with $C_\mathrm{3}$ + $T$ symmetry in the presence of crystal-field splitting.

Kondo Effect in Micron Size Device Fabricated From Flakes of Mn Doped Bi2Se3 Topological Insulator
Vishal K. Maurya, Jeetendra K. Tiwari, S. Ghosh, S. Patnaik
arXiv:2403.08468v1 Announce Type: new Abstract: Single crystals of Mn0.03Bi1.97Se3 were synthesized by modified Bridgman technique and phase purity was confirmed via XRD analysis. EDAX analysis has verified the stoichiometric ratio of elements in the sample. Sample flakes were transferred to the SiO2/Si n-type substrate by mechanical exfoliation technique. Four probe gold contacts were etched with the help of e-beam lithography by masking and lift off process. Resistivity measurement was performed in four probe configurations in 2-300 K temperature range. We report evidence for Kon-do effect in Mn0.03Bi1.97Se3 micro-flakes with Tmin of 14.4 K.

Thermal Hall effect incorporating magnon damping in localized spin systems
Shinnosuke Koyama, Joji Nasu
arXiv:2403.08478v1 Announce Type: new Abstract: We propose a theory for thermal Hall transport mediated by magnons to address the impact of their damping resulting from magnon-magnon interactions in insulating magnets. This phenomenon is anticipated to be particularly significant in systems characterized by strong quantum fluctuations, exemplified by spin-1/2 systems. Employing a nonlinear flavor-wave theory, we analyze a general model for localized electron systems and develop a formulation for thermal conductivity based on a perturbation theory, utilizing bosonic Green's functions with a nonzero self-energy. We derive the expression of the thermal Hall conductivity incorporating magnon damping. To demonstrate the applicability of the obtained representation, we adopt it to two $S=1/2$ quantum spin models on a honeycomb lattice. In calculations for these systems, we make use of the self-consistent imaginary Dyson equation approach at finite temperatures for evaluating the magnon damping rate. In both systems, the thermal Hall conductivity is diminished due to the introduction of magnon damping over a wide temperature range. This effect arises due to the smearing of magnon spectra with nonzero Berry curvatures. We also discuss the relation to the damping of chiral edge modes of magnons. Our formulation can be applied to various localized electron systems as we begin with a general Hamiltonian for these systems. Our findings shed light on a new aspect of topological magnonics emergent from many-body effects and will stimulate further investigations on the impact of magnon damping on topological phenomena.

Study of Physical Characteristics of the New Half-Heusler Alloy BaHgSn by DFT Analysis
A. Jabar, S. Benyoussef, L. Bahmad
arXiv:2403.08483v1 Announce Type: new Abstract: To investigate the physical characteristics of the half-Heusler BaHgSn molecule, we used theoretical calculations within the Density Functional Theory (DFT) framework utilizing the LSDA+mBJ technique in this study. Using the optimal lattice parameters, we discover that half-Heusler BaHgSn exhibits a Dirac semimetal behavior with a band gap of 0.1 eV. Thomas Charpin's numerical first-principles calculation approach was applied to determine the elastic constants of hexagonal BaHgSn alloys. The material's optical characteristics verified its prospective use in infrared-visible devices. According to a thermo-electric properties analysis, at 20x10^18 {\Omega}-1.m-1.s-1, the electrical conductivity reaches its maximum after increasing gradually up to 500 K. Compared to other compounds, these results indicate that BaHgSn has potential for use in opto-electronic and thermo-electric devices.

Stability of Weyl node merging processes under symmetry constraints
Gabriele Naselli, Gy\"orgy Frank, D\'aniel Varjas, Ion Cosma Fulga, Gerg\H{o} Pint\'er, Andr\'as P\'alyi, Viktor K\"onye
arXiv:2403.08518v1 Announce Type: new Abstract: Changes in the number of Weyl nodes in Weyl semimetals occur through merging processes, usually involving a pair of oppositely charged nodes. More complicated processes involving multiple Weyl nodes are also possible, but they typically require fine tuning and are thus less stable. In this work, we study how symmetries affect the allowed merging processes and their stability, focusing on the combination of a two-fold rotation and time-reversal ($C_2\mathcal{T}$) symmetry. We find that, counter-intuitively, processes involving a merging of three nodes are more generic than processes involving only two nodes. Our work suggests that multi-Weyl-merging may be observed in a large variety of quantum materials, and we discuss SrSi$_2$ and bilayer graphene as potential candidates

TopoTB: A software package for calculating the electronic structure and topological properties of the tight-binding model
Xinliang Huang, Fawei Zheng, Ning Hao
arXiv:2403.08615v1 Announce Type: new Abstract: We present TopoTB, a software package written in the Mathematica language, designed to compute electronic structures, topological properties, and phase diagrams based on tight-binding models. TopoTB is user-friendly, with an interactive user interface that enables the tuning of model parameters for fitting the target energy bands in a WYSIWYG way. In addition, TopoTB also includes functionalities for processing results from Density Functional Theory calculations. The outputs of TopoTB are rich and readable, and they can be displayed in various styles. These features make TopoTB a useful tool for the theoretical study of materials.

Reweight-annealing method for calculating the value of partition function via quantum Monte Carlo
Yi-Ming Ding, Nvsen Ma, Gaopei Pan, Chen Cheng, Zheng Yan
arXiv:2403.08642v1 Announce Type: new Abstract: Efficient and accurate algorithm for partition function, free energy and thermal entropy calculations is of great significance in statistical physics and quantum many-body physics. Here we present an unbiased but low-technical-barrier algorithm within the quantum Monte Carlo framework, which has exceptionally high accuracy and no systemic error. Compared with the conventional specific heat integral method and Wang-Landau sampling algorithm, our method can obtain a much more accurate result of the sub-leading coefficient of the entropy. This method can be widely used in both classical and quantum Monte Carlo simulations and is easy to be parallelized on computer.

Room temperature charge density wave in a tetragonal polymorph of Gd2Os3Si5 and study of its origin in the R2T3X5 (R = Rare earth, T = transition metal, X = Si, Ge) series
Vikash Sharma, Sitaram Ramakrishnan, S. S. Jayakrishnan, Surya Rohith Kotla, Bishal Maiti, Claudio Eisele, Harshit Agarwal, Leila Noohinejad, M. Tolkiehn, Dipanshu Bansal, Sander van Smaalen, Arumugam Thamizhavel
arXiv:2403.08660v1 Announce Type: new Abstract: Charge density wave (CDW) systems are proposed to exhibit application potential for electronic and optoelectronic devices. Therefore, identifying new materials that exhibit a CDW state at room temperature is crucial for the development of CDW-based devices. Here, we present a non-layered tetragonal polymorph of Gd2Os3Si5, which exhibits a CDW state at room temperature. Gd2Os3Si5 crystallizes in the U2Mn3Si5-type tetragonal crystal structure with the space group P4/mnc. Single-crystal x-ray diffraction (SXRD) analysis shows that Gd2Os3Si5 possesses an incommensurately modulated structure with modulation wave vector q = (0.53, 0, 0), while the modulation reduces the symmetry to orthorhombic Cccm({\sigma}00)0s0. This differs in contrast to isostructural Sm2Ru3Ge5, where the modulated phase has been reported to possess the superspace symmetry Pm({\alpha} 0 {\gamma})0. However, reinvestigation of Sm2Ru3Ge5 suggests that its modulated crystal structure can alternatively be described by Cccm({\sigma}00)0s0, with modulations similar to Gd2Os3Si5. The magnetic susceptibility, \c{hi}(T), exhibits a maximum at low temperatures that indicates an antiferromagnetic transition at TN = 5.5 K. The \c{hi}(T) furthermore shows an anomaly at around 345 K, suggesting a CDW transition at TCDW = 345 K, that corroborates the result from high-temperature SXRD measurements. Interestingly, R2T3X5 compounds are known to crystallize either in the tetragonal Sc2Fe3Si5 type structure or in the orthorhombic U2Co3Si5 structure type. Not all of the compounds in the R2T3X5 series undergo CDW phase transitions. We find that R2T3X5 compounds will exhibit a CDW transition, if the condition : 0.526 < c/sqrt(ab) < 0.543 is satisfied. We suggest the wave vector-dependent electron-phonon coupling to be the dominant mechanism of CDW formation in the tetragonal polymorph of Gd2Os3Si5.

Antiferromagnetic ordering and glassy nature in NASICON type NaFe$_2$PO$_4$(SO$_4$)$_2$
Manish Kr. Singh, A. K. Bera, Ajay Kumar, S. M. Yusuf, R. S. Dhaka
arXiv:2403.08679v1 Announce Type: new Abstract: We investigate crystal structure and magnetic properties including spin relaxation and magnetocaloric effect in NASICON type NaFe$_2$PO$_4$(SO$_4$)$_2$ sample. The Rietveld refinement of x-ray and neutron diffraction patterns show a rhombohedral crystal structure with the R$\bar{3}$c space group. The core-level spectra confirm the desired oxidation state of constituent elements. The {\it dc}--magnetic susceptibility ($\chi$) behavior in zero field-cooled (ZFC) and field-cooled (FC) modes show the ordering temperature $\approx$50~K. Interestingly, the analysis of temperature dependent neutron diffraction patterns reveal an A-type antiferromagnetic (AFM) structure with the ordered moment of 3.8 $\mu_{B}$/Fe$^{3+}$ at 5~K, and a magnetostriction below $T_{\rm N}=$ 50~K. Further, the peak position in the {\it ac}--$\chi$ is found to be invariant with the excitation frequency supporting the notion of dominating AFM transition. Also, the unsaturated isothermal magnetization curve supports the AFM ordering of the moments; however, the observed coercivity suggests the presence of weak ferromagnetic (FM) correlations at 5~K. On the other hand, a clear bifurcation between ZFC and FC curves of {\it dc}--$\chi$ and the observed decrease in peak height of {\it ac}--$\chi$ with frequency suggest for the complex magnetic interactions. The spin relaxation behavior in thermo-remanent magnetization and aging measurements indicate the glassy states at 5~K. Moreover, the Arrott plots and magnetocaloric analysis reveal the AFM--FM interactions in the sample at lower temperatures.

Evidence of enhanced thermopower from emergent local moments in flatbands of magic-angle twisted bilayer graphene
Ayan Ghosh, Souvik Chakraborty, Ranit Dutta, Adhip Agarwala, K. Watanabe, T. Taniguchi, Sumilan Banerjee, Nandini Trivedi, Subroto Mukerjee, Anindya Das
arXiv:2403.08686v1 Announce Type: new Abstract: Recent experiments on magic-angle twisted bilayer graphene (MATBLG) indicate an unusual coexistence of heavy and light electrons, characteristic of Heavy-Fermion physics. Yet, these experiments lack direct evidence of the existence of local moments associated with the heavy electrons, a key component of Heavy-Fermion physics. Thermopower serves as a sensitive probe for measuring entropy and can, therefore, unveil the presence of local moments by assessing their impact on entropy. In this work, we have carried out comprehensive thermopower studies on MATBLG by varying temperatures ($T$) and magnetic fields ($B$). While the resistance exhibits prominent resistance peaks at integer fillings apart from the Dirac point (DP, $\nu = 0$) and full band filling ($\nu = \pm 4$), the thermopower remains featureless and symmetric to the DP with opposite signs, in complete violation of the Mott formula, even up to $\sim 100K$. This discrepancy indicates that resistance and thermopower are carried by different kinds of carriers. With the expected sign changes at the DP and full band filling, the thermopower demonstrates additional sign changes within the conduction and valence bands around $\nu \sim \pm 1$, persisting from $5K$ to $50K$. These observations cannot be explained solely by thermopower arising from an emergent Heavy-Fermion band picture, which is highly sensitive to temperature. Instead, our data is consistent with the dominant contribution coming from the entropy of the localized moments of heavy electrons. To validate the claim, we studied the thermopower with $B_{\parallel}$ and $B_{\perp}$, revealing a $30\%$ and $50\%$ reduction, respectively, and attributed to the partial polarization of the local moments (spin/valley), resulting in decreased entropy. Our results highlight the thermopower contribution from local moments and establish the Heavy-Fermion physics in MATBLG.

Boundary geometry controls topological defect transitions that determine lumen nucleation in embryonic development
Pamela C. Guruciaga, Takafumi Ichikawa, Takashi Hiiragi, Anna Erzberger
arXiv:2403.08710v1 Announce Type: new Abstract: Topological defects determine the collective properties of anisotropic materials. How their configurations are controlled is not well understood however, especially in 3D, where bulk-surface coupling can render the geometry of confining boundaries relevant. This is particularly important in living matter, where 2D topological defects have been linked to essential biological functions, whereas the role of 3D defects is unclear. Motivated by multicellular systems interacting with extracellular boundaries, we consider a polar fluid confined within curved boundaries imposing weak surface anchoring. We report a novel charge-preserving transition between different defect configurations, controlled by the boundary shape, and invariant to changes in the material parameters. We test if this geometry-driven transition occurs in confined multicellular systems and investigate the biological role of 3D polar defects in the mouse epiblast -- an embryonic tissue consisting of apico-basally polarised cells. We find that fluid-filled lumina -- structures essential for subsequent embryonic development -- tend to form near defect positions of polar fluids in embryo-like confinement geometries. Moreover, by experimentally perturbing embryo shape beyond the transition point, we trigger the formation of additional lumen nucleation sites at the predicted position. Thus, our work reveals how boundary geometry controls polar defects, and how embryos use this mechanism for shape-dependent lumen formation. Because this defect control principle is independent of specific material properties, we expect it to apply universally to systems with orientational order.

Driving non-trivial quantum phases in conventional semiconductors with intense excitonic fields
Vivek Pareek, David R. Bacon, Xing Zhu, Yang-Hao Chan, Fabio Bussolotti, Nicholas S. Chan, Joel P\'erez Urquizo, Kenji Watanabe, Takashi Taniguchi, Michael K. L. Man, Julien Mad\'eo, Diana Y. Qiu, Kuan Eng Johnson Goh, Felipe H. da Jornada, Keshav M. Dani
arXiv:2403.08725v1 Announce Type: new Abstract: Inducing novel quantum phases and topologies in materials using intense light fields is a key objective of modern condensed matter physics, but nonetheless faces significant experimental challenges. Alternately, theory predicts that in the dense limit, excitons - collective excitations composed of Coulomb-bound electron-hole pairs - could also drive exotic quantum phenomena. However, the direct observation of these phenomena requires the resolution of electronic structure in momentum space in the presence of excitons, which became possible only recently. Here, using time- and angle-resolved photoemission spectroscopy of an atomically thin semiconductor in the presence of a high-density of resonantly and coherently photoexcited excitons, we observe the Bardeen-Cooper-Schrieffer (BCS) excitonic state - analogous to the Cooper pairs of superconductivity. We see the valence band transform from a conventional paraboloid into a Mexican-hat like Bogoliubov dispersion - a hallmark of the excitonic insulator phase; and we observe the recently predicted giant exciton-driven Floquet effects. Our work realizes the promise that intense bosonic fields, other than photons, can also drive novel quantum phenomena and phases in materials.

Interface Design Beyond Epitaxy: Oxide Heterostructures Comprising Symmetry-forbidden Interfaces
Hongguang Wang, Varun Harbola, Yu-Jung Wu, Peter A. van Aken, Jochen Mannhart
arXiv:2403.08736v1 Announce Type: new Abstract: Epitaxial growth of thin-film heterostructures is generally considered the most successful procedure to obtain interfaces of excellent structural and electronic quality between three-dimensional materials. However, these interfaces can only join material systems with crystal lattices of matching symmetries and lattice constants. We present a novel category of interfaces, the fabrication of which is membrane-based and does not require epitaxial growth. These interfaces therefore overcome limitations imposed by epitaxy. Leveraging the additional degrees of freedom gained, we demonstrate atomically clean interfaces between three-fold symmetric sapphire and four-fold symmetric SrTiO3. Atomic-resolution imaging reveals structurally well-defined interfaces with a novel moir\'e-type reconstruction.

Turbulence from First Principles
Chris Scott
arXiv:2403.07950v1 Announce Type: cross Abstract: We provide a first-principles approach to turbulence by employing the electrodynamics of continuous media at the viscous limit to recover the Navier-Stokes equations. We treat oscillators with two orthogonal angular momenta as a spin network with properties applicable to the Kolmogorov-Arnold-Moser (KAM) theorem. The microscopic viscous limit has an irreducible representation that includes $O(3)$ expansion terms for a radiation-dominated fluid with a Friedmann-Lemaitre-Robertson-Walker (FLRW) metric, equivalent to an oriented toroidal de Sitter space. The turbulence solution in $\mathbb{R}^{3,1}$ lies on 6-choose-3 de Sitter intersections of three orthogonal $n$-tori.

Zero modes of velocity field and topological invariant in quantum torus
Annan Fan, Shi-Dong Liang
arXiv:2403.08232v1 Announce Type: cross Abstract: We propose the velocity field approach to characterize topological invariants of quantum states. We introduce the indexes of the velocity field flow based on the zero modes of the velocity field and find that these zero modes play the role of effective topological charges or defects linking to Euler characteristic by the Poincar\'{e}-Hopf theorem. The global property of the indexes is topological invariants against the parameter deformation. We demonstrate this approach by the quantum torus model and compare the topological invariant with that obtained from the Chern number. We find that the physical mechanism of the topological invariant based on the zero modes of the velocity field is different from that of the topological invariant by the Chern number. The topological invariant characterized by the velocity field describes a homeomorphic topological invariant associated with the zero modes on the submanifold of the base manifold of the SU(2)-fibre bundle for quantum torus, whereas the Chern number characterizes a homotopy invariant associated with the exceptional points in the Brillouin zone. We also propose the generalized winding number in terms of the velocity field for both Hermitian and non-Hermitian systems. This gives a connection between the zero mode and winding number in the velocity space. These results enrich the topological invariants of quantum states and promises us a novel insight to understanding topological invariants of quantum states as well as expected to be further applied in more generic models.

Intense and Stable Blue Light Emission from CsPbBr$_3$/Cs$_4$PbBr$_6$ Heterostructures Embedded in Transparent Nanoporous Films
Carlos Romero-Perez, Natalia Fernandez Delgado, Miriam Herrera Collado, Mauricio E. Calvo, Hernan Miguez
arXiv:2403.08315v1 Announce Type: cross Abstract: Lead halide perovskite nanocrystals are attractive for light emitting devices both as electroluminescent and color converting materials, since they combine intense and narrow emissions with good charge injection and transport properties. However, most perovskite nanocrystals shine at green and red wavelengths, the observation of intense and stable blue emission still being a challenging target. In this work, we report a method to attain intense and enduring blue emission (470-480 nm), with a photoluminescence quantum yield (PLQY) of 40%, originated from very small CsPbBr$_3$ nanocrystals (diameter<3nm) formed by controllably exposing Cs$_4$PbBr$_6$ to humidity. This process is mediated by the void network of a mesoporous transparent scaffold in which the zero-dimensional (0D) Cs$_4$PbBr$_6$ lattice is embedded, which allows the fine control over water adsorption and condensation that determines the optimization of the synthetic procedure and, eventually, the nanocrystal size. By temperature dependent photoemission analysis of samples with different [CsPbBr$_3$]/[Cs$_4$PbBr$_6$] volume ratios, we show that the bright blue emission observed results from the efficient charge transfer to the CsPbBr$_3$ inclusions from the Cs$_4$PbBr$_6$ host. Our approach provides a means to attain highly efficient transparent blue light emitting films that complete the palette offered by perovskite nanocrystals for lighting and display applications.

Environment-Induced Information Scrambling Transition with Charge Conservations
Pengfei Zhang, Zhenhua Yu
arXiv:2403.08622v1 Announce Type: cross Abstract: In generic closed quantum systems, the complexity of operators increases under time evolution governed by the Heisenberg equation, reflecting the scrambling of local quantum information. However, when systems interact with an external environment, the system-environment coupling allows operators to escape from the system, inducing a dynamical transition between the scrambling phase and the dissipative phase. This transition is known as the environment-induced information scrambling transition, originally proposed in Majorana fermion systems. In this work, we advance this dicovery by investigating the transition in charge-conserved systems with space-time randomness. We construct solvable Brownian Sachdev-Ye-Kitaev models of complex fermions coupled to an environment, enabling the analytical computation of operator growth. We determine the critical dissipation strength, which is proportional to $n(1-n)$ with $n$ being the density of the complex fermions, arising from the suppression in the quantum Lyapunov exponent due to the Pauli blockade in the scattering process. We further analyze the density dependence of maximally scrambled operators at late time. Our results shed light on the intriguing interplay between information scrambling, dissipation, and conservation laws.

On the geometric phase and its role in the design of elastic topological materials
Mohit Kumar, Fabio Semperlotti
arXiv:2403.08711v1 Announce Type: cross Abstract: The geometric phase provides important mathematical insights to understand the occurrence and evolution of the dynamic response in a diverse spectrum of systems ranging from quantum to classical mechanics. While the concept of geometric phase, which is an additional phase factor occurring in dynamical systems, holds the same meaning across different fields of application, its use and interpretation can acquire important nuances specific to the system of interest. In recent years, the development of the concept of quantum topological materials and its extension to classical mechanical systems have renewed the interest in the study of the geometric phase. This study reviews the concept of geometric phase and discusses, by means of either established or original results, its role in the design of elastic materials. Concepts of differential geometry and topology are put forward to provide a theoretical understanding of the geometric phase and its connection to the physical properties of the system. Then, the concept of geometric phase is applied to different types of elastic waveguides to explain how either topologically trivial or non-trivial behavior can emerge based on a proper geometric design of the waveguide.

Isotope effects in supercooled H$_2$O and D$_2$O and a corresponding-states-like rescaling of the temperature and pressure
Greg A. Kimmel
arXiv:2403.08722v1 Announce Type: cross Abstract: Water shows anomalous properties that are enhanced upon supercooling. The unusual behavior is observed in both H$_2$O and D$_2$O, however with different temperature dependences for the two isotopes. It is often noted that comparing the properties of the isotopes at two different temperatures (i.e., a temperature shift) approximately accounts for many of the observations with a temperature shift of 7.2 K in the temperature of maximum density being the most well-known example. However, the physical justification for such a shift is unclear. Motivated by recent work demonstrating a corresponding-states-like rescaling for water properties in three classical water models that all exhibit a liquid-liquid transition and critical point (B. Uralcan, et al., J. Chem. Phys. 150, 064503 (2019)), the applicability of this approach for reconciling the differences in temperature- and pressure-dependent thermodynamic properties of H$_2$O and D$_2$O is investigated here. Utilizing previously published data and equations-of-state for H$_2$O and D$_2$O, we show that the available data and models for these isotopes are consistent with such a low temperature correspondence. These observations provide support for the hypothesis that a liquid-liquid critical point, which is predicted to occur at low temperatures and high pressures, is the origin of many of water's anomalies.

Phase-ordering kinetics in the Allen-Cahn (Model A) class: universal aspects elucidated by electrically-induced transition in liquid crystals
Renan A. L. Almeida, Kazumasa A. Takeuchi
arXiv:2107.09043v3 Announce Type: replace Abstract: The two-dimensional (2d) Ising model is the statistical physics textbook example for phase transitions and their kinetics. Quenched through the Curie point with Glauber rates, the late-time description of the ferromagnetic domain coarsening finds its place at the scalar sector of the Allen-Cahn (Model A) class. Resisting exact results sought since Lifshitz's account in 1962, central quantities in 2d Model A $-$ most scaling exponents and correlation functions $-$ remain known up to approximate theories whose disparate outcomes urge experimental assessment. Here, we perform such assessment from a comprehensive study of the coarsening of 2d twisted nematic liquid crystals whose kinetics is induced by a super-fast switching from a spatiotemporally chaotic state to a two-phase concurrent, equilibrium one. Tracking the dynamics via optical microscopy, we firstly show the sharp evidence of well-established Model A aspects, such as the dynamic exponent $z=2$ and the dynamic scaling hypothesis, to then move forward. We confirm the Bray-Humayun theory for Porod's regime describing intradomain length scales of spatial correlators, and show that their nontrivial decay beyond that regime is captured in a free-from-parameter fashion by Gaussian theories. These paradigmatic theories, however, do not perform well for time-related Model A statistics. We reveal that the collapsed form of two-time correlators is best accounted for by the local scaling invariance theory, along with the Fisher-Huse conjecture. We also suggest the true value for the local persistence exponent, in disfavour of Gaussian models, and extract a universal fractal dimension for the morphology of persistence clusters that is notably close to the golden ratio. Given its accuracy and possibilities, this experimental setup may work as a prototype to address universality issues in the realm of nonequilibrium systems.

From the XXZ chain to the integrable Rydberg-blockade ladder via non-invertible duality defects
Luisa Eck, Paul Fendley
arXiv:2302.14081v4 Announce Type: replace Abstract: Strongly interacting models often possess "dualities" subtler than a one-to-one mapping of energy levels. The maps can be non-invertible, as apparent in the canonical example of Kramers and Wannier. We analyse an algebraic structure common to the XXZ spin chain and three other models: Rydberg-blockade bosons with one particle per square of a ladder, a three-state antiferromagnet, and two Ising chains coupled in a zigzag fashion. The structure yields non-invertible maps between the four models while also guaranteeing all are integrable. We construct these maps explicitly utilising topological defects coming from fusion categories and the lattice version of the orbifold construction, and use them to give explicit conformal-field-theory partition functions describing their critical regions. The Rydberg and Ising ladders also possess interesting non-invertible symmetries, with the spontaneous breaking of one in the former resulting in an unusual ground-state degeneracy.

Gap engineering and wave function symmetry in C and BN armchair nanoribbons
Elisa Serrano Richaud, Sylvain Latil, Hakim Amara, Lorenzo Sponza
arXiv:2302.14432v2 Announce Type: replace Abstract: Many are the ways of engineering the band gap of nanoribbons including application of stress, electric field and functionalization of the edges. In this article, we investigate separately the effects of these methods on armchair graphene and boron nitride nanoribbons. By means of density functional theory calculations, we show that, despite their similar structure, the two materials respond in opposite ways to these stimuli. By treating them as perturbations of a heteroatomic ladder model based on the tight-binding formalism, we connect the two behaviours to the different symmetries of the top valence and bottom conduction wave functions. These results indicate that opposite and complementary strategies are preferable to engineer the gapwidth of armchair graphene and boron nitride nanoribbons.

The discovery of three-dimensional Van Hove singularity
Wenbin Wu, Zeping Shi, Mykhaylo Ozerov, Yuhan Du, Yuxiang Wang, Xiao-Sheng Ni, Xianghao Meng, Xiangyu Jiang, Guangyi Wang, Congming Hao, Xinyi Wang, Pengcheng Zhang, Chunhui Pan, Haifeng Pan, Zhenrong Sun, Run Yang, Yang Xu, Yusheng Hou, Zhongbo Yan, Cheng Zhang, Hai-Zhou Lu, Junhao Chu, Xiang Yuan
arXiv:2304.07043v2 Announce Type: replace Abstract: Arising from the extreme/saddle point in electronic bands, Van Hove singularity (VHS) manifests divergent density of states (DOS) and induces various new states of matter such as unconventional superconductivity. VHS is believed to exist in one and two dimensions, but rarely found in three dimension (3D). Here, we report the discovery of 3D VHS in a topological magnet EuCd2As2 by magneto-infrared spectroscopy. External magnetic fields effectively control the exchange interaction in EuCd2As2, and shift 3D Weyl bands continuously, leading to the modification of Fermi velocity and energy dispersion. Above the critical field, the 3D VHS forms and is evidenced by the abrupt emergence of inter-band transitions, which can be quantitatively described by the minimal model of Weyl semimetals. Three additional optical transitions are further predicted theoretically and verified in magneto-near-infrared spectra. Our results pave the way to exploring VHS in 3D systems and uncovering the coordination between electronic correlation and the topological phase.

A generative artificial intelligence framework based on a molecular diffusion model for the design of metal-organic frameworks for carbon capture
Hyun Park, Xiaoli Yan, Ruijie Zhu, E. A. Huerta, Santanu Chaudhuri, Donny Cooper, Ian Foster, Emad Tajkhorshid
arXiv:2306.08695v2 Announce Type: replace Abstract: Metal-organic frameworks (MOFs) exhibit great promise for CO2 capture. However, finding the best performing materials poses computational and experimental grand challenges in view of the vast chemical space of potential building blocks. Here, we introduce GHP-MOFassemble, a generative artificial intelligence (AI), high performance framework for the rational and accelerated design of MOFs with high CO2 adsorption capacity and synthesizable linkers. GHP-MOFassemble generates novel linkers, assembled with one of three pre-selected metal nodes (Cu paddlewheel, Zn paddlewheel, Zn tetramer) into MOFs in a primitive cubic topology. GHP-MOFassemble screens and validates AI-generated MOFs for uniqueness, synthesizability, structural validity, uses molecular dynamics simulations to study their stability and chemical consistency, and crystal graph neural networks and Grand Canonical Monte Carlo simulations to quantify their CO2 adsorption capacities. We present the top six AI-generated MOFs with CO2 capacities greater than 2 $m mol/g$, i.e., higher than 96.9% of structures in the hypothetical MOF dataset.

Strongly Interacting Phases in Twisted Bilayer Graphene at the Magic Angle
Khagendra Adhikari, Kangjun Seo, K. S. D. Beach, Bruno Uchoa
arXiv:2308.03843v2 Announce Type: replace Abstract: Twisted bilayer graphene near the magic angle is known to have a cascade of insulating phases at integer filling factors of the low-energy bands. In this Letter we address the nature of these phases through an unrestricted, large-scale Hartree-Fock calculation on the lattice that self-consistently accounts for all electronic bands. Using numerically unbiased methods, we show that Coulomb interactions produce ferromagnetic insulating states at integer fillings $\nu\in[-3,3]$ with maximal spin polarization $M_{\text{FM}}=4-|\nu|$. We find that the $\nu=0$ state is a pure ferromagnet, whereas all other insulating states are spin-valley polarized. At odd filling factors $|\nu|=1,3$ those states have a quantum anomalous Hall effect with Chern number $\mathcal{C}=1$. Except for the $\nu=0,-2$ states, all other integer fillings have insulating phases with additional sublattice symmetry breaking and antiferromagnetism in the remote bands. We map the metal-insulator transitions of these phases as a function of the effective dielectric constant. Our results establish the importance of large-scale lattice calculations to faithfully determine the ground states of TBG at integer fillings.

Support-based transfer and contacting of individual nanomaterials for in-situ nanoscale investigations
Simon Hettler, Mohammad Furqan, Raul Arenal
arXiv:2309.14060v2 Announce Type: replace Abstract: Although in-situ transmission electron microscopy (TEM) of nanomaterials has been gaining importance in recent years, difficulties in sample preparation have limited the number of studies on electrical properties. Here, a support-based preparation method of individual 1D and 2D materials is presented, which yields a reproducible sample transfer for electrical investigation by in-situ TEM. Using a mechanically rigid support grid allows the reproducible transfer and contacting to in-situ chips by focused ion beam with minimum damage and contamination. The transfer quality is assessed by exemplary studies of different nanomaterials, including a monolayer of WS2. Preliminary results from in-situ test experiments give an overview of possible studies, which concern the interplay between structural properties and electrical characteristics on the individual nanomaterial level as well as failure analysis under electrical current or studies of electromigration, Joule heating and related effects. The TEM measurements can be enriched by additional correlative microscopy techniques, which allow the study with a spatial resolution in the range of a few microns. Although developed for in-situ TEM, the present transfer method is also applicable to transferring nanomaterials to similar chips for performing further studies or even for using them in potential electrical/optoelectronic/sensing devices.

Quenched pair breaking by interlayer correlations as a key to superconductivity in La$_3$Ni$_2$O$_7$
Siheon Ryee, Niklas Witt, Tim O. Wehling
arXiv:2310.17465v2 Announce Type: replace Abstract: The recent discovery of superconductivity in La$_3$Ni$_2$O$_7$ with $T_\mathrm{c} \simeq 80~\mathrm{K}$ under high pressure opens up a new route to high-$T_\mathrm{c}$ superconductivity. This material realizes a bilayer square lattice model featuring a strong interlayer hybridization unlike many unconventional superconductors. A key question in this regard concerns how electronic correlations driven by the interlayer hybridization affect the low-energy electronic structure and the concomitant superconductivity. Here, we demonstrate using a cluster dynamical mean-field theory that the interlayer electronic correlations (IECs) induce a Lifshitz transition resulting in a change of Fermi surface topology. By solving an appropriate gap equation, we further show that the dominant pairing instability (intraorbital $s$-wave/interorbital $d_{x^2-y^2}$-wave, or $s \pm$-wave in a bonding-antibonding basis) is enhanced by the IECs. The underlying mechanism is the quenching of a strong ferromagnetic channel, resulting from the Lifshitz transition driven by the IECs. Based on this picture, we provide a possible reason of why superconductivity emerges only under high pressure.

Native point defects in HgCdTe infrared detector material: Identifying deep centers from first principles
Wei Chen, Gian-Marco Rignanese, Jifeng Liu, Geoffroy Hautier
arXiv:2311.05283v2 Announce Type: replace Abstract: We investigate the native point defects in the long-wavelength infrared (LWIR) detector material Hg$_{0.75}$Cd$_{0.25}$Te using a dielectric-dependent hybrid density functional combined with spin-orbit coupling. Characterizing these point defects is essential as they are responsible for intrinsic doping and nonradiative recombination centers in the detector material. The dielectric-dependent hybrid functional allows for an accurate description of the band gap ($E_g$) for Hg$_{1-x}$Cd$_{x}$Te (MCT) over the entire compositional range, a level of accuracy challenging with standard hybrid functionals. Our comprehensive examination of the native point defects confirms that cation vacancies $V_\text{Hg(Cd)}$ are the primary sources of $p$-type conductivity in the LWIR material given their low defect formation energies and the presence of a shallow acceptor level ($-$/0) near the valence-band maximum (VBM). In addition to the shallow acceptor level, the cation vacancies exhibit a deep charge transition level (2$-$/$-$) situated near the midgap, characteristic of nonradiative recombination centers. Our results indicate that Hg interstitial could also be a deep center in the LWIR MCT through a metastable configuration under the Hg-rich growth conditions. While an isolated Te antisite does not show deep levels, the formation of $V_\text{Hg}$-Te$_\text{Hg}$ defect complex introduces a deep acceptor level within the band gap.

Robust Dipolar Layers between Organic Semiconductors and Silver for Energy-Level Alignment
Tom\'a\v{s} Kraj\v{n}\'ak, Veronika Star\'a, Pavel Proch\'azka, Jakub Planer, Tom\'a\v{s} Sk\'ala, Matthias Blatnik, Jan \v{C}echal
arXiv:2312.08233v2 Announce Type: replace Abstract: The interface between a metal electrode and an organic semiconductor (OS) layer has a defining role in the properties of the resulting device. To obtain a desired performance, interlayers are introduced to modify the adhesion and growth of OS and enhance the efficiency of charge transport through the interface. However, the employed interlayers face common challenges, including a lack of electric dipoles to tune the mutual position of energy levels, being too thick for efficient electronic transport, or being prone to intermixing with subsequently deposited OS layers. Here, we show that monolayers of 1,3,5-tris(4 carboxyphenyl)benzene (BTB) with fully deprotonated carboxyl groups on silver substrates form a compact layer resistant to intermixing while mediating energy level alignment and showing a large insensitivity to substrate termination. Employing a combination of surface-sensitive techniques, i.e., low-energy electron microscopy and diffraction, X-ray photoelectron spectroscopy, and scanning tunneling microscopy, we have comprehensively characterized the compact layer and proven its robustness against mixing with the subsequently deposited organic semiconductor layer. DFT calculations show that the robustness arises from a strong interaction of carboxylate groups with the Ag surface, and thus, the BTB in the first layer is energetically favored. Synchrotron radiation photoelectron spectroscopy shows that this layer displays considerable electrical dipoles that can be utilized for work function engineering and electronic alignment of molecular frontier orbitals with respect to the substrate Fermi level. Our work thus provides a widely applicable molecular interlayer and general insights necessary for engineering of charge injection layers for efficient organic electronics.

Anisotropic skyrmion and multi-$q$ spin dynamics in centrosymmetric Gd$_2$PdSi$_3$
M. Gomil\v{s}ek, T. J. Hicken, M. N. Wilson, K. J. A. Franke, B. M. Huddart, A. \v{S}tefan\v{c}i\v{c}, S. J. R. Holt, G. Balakrishnan, D. A. Mayoh, M. T. Birch, S. H. Moody, H. Luetkens, Z. Guguchia, M. T. F. Telling, P. J. Baker, S. J. Clark, T. Lancaster
arXiv:2312.17323v2 Announce Type: replace Abstract: Skyrmions are particle-like vortices of magnetization with non-trivial topology, which are usually stabilized by Dzyaloshinskii-Moriya interactions (DMI) in noncentrosymmetric bulk materials. Exceptions are centrosymmetric Gd- and Eu-based skyrmion-lattice (SkL) hosts with net-zero DMI, where both the SkL stabilization mechanisms and magnetic ground states remain controversial. We address these by investigating both static and dynamic spin properties of the centrosymmetric SkL host Gd$_2$PdSi$_3$ using muon spectroscopy ($\mu$SR). We find that spin fluctuations in its non-coplanar SkL phase are highly anisotropic, implying that spin anisotropy plays a prominent role in stabilizing this phase. We also observe strongly-anisotropic spin dynamics in the ground-state (IC-1) incommensurate magnetic phase of the material, indicating that it is a meron-like multi-$q$ structure. In contrast, the higher-field, coplanar IC-2 phase is found to be single-$q$ with nearly-isotropic spin dynamics.

Measurement-induced phase transitions by matrix product states scaling
Guillaume Cecile, Hugo L\'oio, Jacopo De Nardis
arXiv:2402.13160v2 Announce Type: replace Abstract: We study the time evolution of long quantum spin chains subjected to continuous monitoring via matrix product states (MPS) at fixed bond dimension, with the Time-Dependent Variational Principle (TDVP) algorithm. The latter gives an effective classical non-linear evolution with a conserved charge, which approximates the real quantum evolution up to an error. We show that the error rate displays a phase transition in the monitoring strength, which can be well detected by scaling analysis with relatively low values of bond dimensions. The method allows for an efficient numerical determination of the critical measurement-induced phase transition parameters in many-body quantum systems. Moreover, in the presence of U(1) global spin charge, we show the existence of a charge-sharpening transition well separated from the entanglement transition which we detect by studying the charge fluctuations of a local sub-part of the system at very large times. Our work substantiates the TDVP time evolution as a method to identify measured-induced phase transitions in systems of arbitrary dimensions and sizes.

Layer Coherence Origin of Intrinsic Planar Hall Effect in 2D Limit
Huiyuan Zheng, Dawei Zhai, Cong Xiao, Wang Yao
arXiv:2402.17166v2 Announce Type: replace Abstract: The intrinsic planar Hall effect has attracted intensive interest inspired by recent experiments. Existing theories of this effect require three dimensional orbital motion, or strong spin-orbit coupling of certain forms, which do not exist in van der Waals thin films. Here, we uncover a new origin of the planar Hall effect - as an intrinsic property of layer coherent electrons - that allows its presence even in bilayer and trilayer atomically thin limit. As examples, we show that the effect can be triggered by strain and interlayer sliding respectively in twisted bilayer graphene and trilayer transition metal dichalcogenides, where the effect features rich tunability and even stronger magnitude than those induced by topological nodal structures in bulk materials. The layer mechanism also provides a new route towards quantized Hall response upon a topological phase transition induced by in-plane magnetic field. These results unveil the unexplored potential of quantum layertronics and moir\'e flat band for planar Hall transport.

Double magnetic transition, complex field-induced phases, and large magnetocaloric effect in the frustrated garnet compound Mn$_{3}$Cr$_{2}$Ge$_{3}$O$_{12}$
S. Mohanty, A. Magar, Vikram Singh, S. S. Islam, S. Guchhait, A. Jain, S. M. Yusuf, A. A. Tsirlin, R. Nath
arXiv:2403.02082v2 Announce Type: replace Abstract: A detailed study of the magnetic and magnetocaloric properties of a garnet compound Mn$_{3}$Cr$_{2}$Ge$_{3}$O$_{12}$ is carried out using x-ray diffraction, magnetization, heat capacity, and neutron diffraction measurements as well as \textit{ab initio} band-structure calculations. This compound manifests two successive magnetic transitions at $T_{\rm N1} \simeq 4.5$ K and $T_{\rm N2} \simeq 2.7$ K. Neutron powder diffraction experiments reveal that these two transitions correspond to the collinear and non-collinear antiferromagnetic ordering of the nonfrustrated Cr$^{3+}$ and frustrated Mn$^{2+}$ sublattices, respectively. The interactions within each of the Cr and Mn sublattices are antiferromagnetic, while the inter-sublattice interactions are ferromagnetic. The $H-T$ phase diagram is quite complex and displays multiple phases under magnetic field, which can be attributed to the frustrated nature of the spin lattice. Mn$_{3}$Cr$_{2}$Ge$_{3}$O$_{12}$ shows a large magnetocaloric effect with a maximum value of isothermal entropy change $\Delta S_{\rm m} \simeq -23$ J/kg-K and adiabatic temperature change $\Delta T_{\rm ad} \simeq 9$ K for a field change of 7 T. Further, a large value of the relative cooling power ($RCP \simeq 360$ J/kg) demonstrates the promise of using this compound in magnetic refrigeration.

Implementation and characterization of the dice lattice in the electron quantum simulator
Camillo Tassi, Dario Bercioux
arXiv:2403.06040v2 Announce Type: replace Abstract: Materials featuring touching points, localized states, and flat bands are of great interest in condensed matter and artificial systems due to their implications in topology, quantum geometry, superconductivity, and interactions. In this theoretical study, we propose the experimental realization of the dice lattice with adjustable parameters by arranging carbon monoxide molecules on a two-dimensional electron system at a (111) copper surface. First, we develop a theoretical framework to obtain the spectral properties within a nearly free electron approximation and then compare them with tight-binding calculations. Our investigation reveals that the high mobility of Shockley state electrons enables an accurate theoretical description of the artificial lattice using a next-nearest-neighbor tight-binding model, resulting in the emergence of a touching point, a quasi-flat band, and localized lattice site behavior in the local density of states. Additionally, we present theoretical results for a long-wavelength low-energy model that accounts for next-nearest-neighbor hopping terms. Furthermore, we theoretically examine the model's behavior under an external magnetic field by employing Peierl's substitution, a commonly used technique in theoretical physics to incorporate magnetic fields into lattice models. Our theoretical findings suggest that, owing to the exceptional electron mobility, the highly degenerate eigenenergy associated with the Aharonov-Bohm caging mechanism may not manifest in the proposed experiment.

Ghost Martin-Siggia-Rose (MSR) applications to Kardar-Parizi-Zhang (KPZ) equation with non-linear noise
Garry Goldstein
arXiv:2403.06481v2 Announce Type: replace Abstract: In this work we modify the Kardar-Parisi-Zhang (KPZ) equation for growing surfaces to include the effect of surface tilt on the noise (that is have non-linearly coupled noise). We introduce ghost Martin-Siggia-Rose (gMSR) action for the KPZ equation with Faddeev-Popov ghosts to compute an auxiliary functional determinant. We integrate out the Faddeev-Popov ghosts to leading order and the auxiliary MSR Lagrange multiplierexactly to obtain and action for the height. We analyze it within the gaussian, meanfield and Landau free energy like approximations and find various instabilities to rough surfaces.

Skyrmion flow in periodically modulated channels
Klaus Raab, Maurice Schmitt, Maarten A. Brems, Jan Roth\"orl, Fabian Kammerbauer, Sachin Krishnia, Mathias Kl\"aui, Peter Virnau
arXiv:2403.07397v2 Announce Type: replace Abstract: Magnetic skyrmions, topologically stabilized chiral magnetic textures with particle-like properties have so far primarily been studied statically. Here, we experimentally investigate the dynamics of skyrmion ensembles in metallic thin film conduits where they behave as quasi-particle fluids. By exploiting our access to the full trajectories of all fluid particles by means of time-resolved magneto-optical Kerr microscopy, we demonstrate that boundary conditions of skyrmion fluids can be tuned by modulation of the channel geometry. We observe as a function of channel width deviations from classical flow profiles even into the no- or partial-slip regime. Unlike conventional colloids, the skyrmion Hall effect can also introduce transversal flow-asymmetries and even local motion of single skyrmions against the driving force which we explore with particle-based simulations, demonstrating the unique properties of skyrmion liquid flow that uniquely deviates from previously known behavior of other quasi-particles.

Anyon condensation and the color code
Markus S. Kesselring, Julio C. Magdalena de la Fuente, Felix Thomsen, Jens Eisert, Stephen D. Bartlett, Benjamin J. Brown
arXiv:2212.00042v2 Announce Type: replace-cross Abstract: The manipulation of topologically-ordered phases of matter to encode and process quantum information forms the cornerstone of many approaches to fault-tolerant quantum computing. Here we demonstrate that fault-tolerant logical operations in these approaches can be interpreted as instances of anyon condensation. We present a constructive theory for anyon condensation and, in tandem, illustrate our theory explicitly using the color-code model. We show that different condensation processes are associated with a general class of domain walls, which can exist in both space- and time-like directions. This class includes semi-transparent domain walls that condense certain subsets of anyons. We use our theory to classify topological objects and design novel fault-tolerant logic gates for the color code. As a final example, we also argue that dynamical `Floquet codes' can be viewed as a series of condensation operations. We propose a general construction for realising planar dynamically driven codes based on condensation operations on the color code. We use our construction to introduce a new Calderbank-Shor Steane-type Floquet code that we call the Floquet color code.

Topological error correcting processes from fixed-point path integrals
Andreas Bauer
arXiv:2303.16405v3 Announce Type: replace-cross Abstract: We propose a unifying paradigm for analyzing and constructing topological quantum error correcting codes as dynamical circuits of geometrically local channels and measurements. To this end, we relate such circuits to discrete fixed-point path integrals in Euclidean spacetime, which describe the underlying topological order: If we fix a history of measurement outcomes, we obtain a fixed-point path integral carrying a pattern of topological defects. As an example, we show that the stabilizer toric code, subsystem toric code, and CSS Floquet code can be viewed as one and the same code on different spacetime lattices, and the honeycomb Floquet code is equivalent to the CSS Floquet code under a change of basis. We also use our formalism to derive two new error-correcting codes, namely a Floquet version of the $3+1$-dimensional toric code using only 2-body measurements, as well as a dynamic code based on the double-semion string-net path integral.

Detecting defect dynamics in relativistic field theories far from equilibrium using topological data analysis
Viktoria Noel, Daniel Spitz
arXiv:2312.04959v2 Announce Type: replace-cross Abstract: We study nonequilibrium dynamics of relativistic $N$-component scalar field theories in Minkowski space-time in a classical-statistical regime, where typical occupation numbers of modes are much larger than unity. In this strongly correlated system far from equilibrium, the role of different phenomena such as nonlinear wave propagation and defect dynamics remains to be clarified. We employ persistent homology to infer topological features of the nonequilibrium many-body system for different numbers of field components $N$ via a hierarchy of cubical complexes. Specifically, we show that the persistent homology of local energy density fluctuations can give rise to signatures of self-similar scaling associated with topological defects, distinct from the scaling behaviour of nonlinear wave modes. This contributes to the systematic understanding of the role of topological defects for far-from-equilibrium time evolutions of nonlinear many-body systems.

Found 9 papers in prb
Date of feed: Thu, 14 Mar 2024 04:17:11 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)

Multifrequency corner states in acoustic second-order topological insulators
Weibai Li, Guoxing Lu, and Xiaodong Huang
Author(s): Weibai Li, Guoxing Lu, and Xiaodong Huang

Second-order topological insulators possess unique boundary states beyond the conventional bulk-boundary correspondence, which provides opportunities for multidimensional wave manipulation in electronic and acoustic systems. This paper develops an acoustic second-order topological insulator by sonic…

[Phys. Rev. B 109, 104308] Published Wed Mar 13, 2024

Magnetic and magnetotransport properties in the vanadium-based kagome metals ${\mathrm{DyV}}_{6}{\mathrm{Sn}}_{6}$ and ${\mathrm{HoV}}_{6}{\mathrm{Sn}}_{6}$
Xiang-Yu Zeng, Huan Wang, Xiao-Yan Wang, Jun-Fa Lin, Jing Gong, Xiao-Ping Ma, Kun Han, Yi-Ting Wang, Zheng-Yi Dai, and Tian-Long Xia
Author(s): Xiang-Yu Zeng, Huan Wang, Xiao-Yan Wang, Jun-Fa Lin, Jing Gong, Xiao-Ping Ma, Kun Han, Yi-Ting Wang, Zheng-Yi Dai, and Tian-Long Xia

Recently, the vanadium-based kagome metals ${\mathrm{RV}}_{6}{\mathrm{Sn}}_{6}$ $(\mathrm{R}=\text{rare-earth})$ have attracted wide attention due to their novel magnetism and nontrivial topological properties. In this paper, the ${\mathrm{DyV}}_{6}{\mathrm{Sn}}_{6}$ and ${\mathrm{HoV}}_{6}{\mathrm{…

[Phys. Rev. B 109, 104412] Published Wed Mar 13, 2024

Coulomb-driven band unflattening suppresses $K$-phonon pairing in moiré graphene
Glenn Wagner, Yves H. Kwan, Nick Bultinck, Steven H. Simon, and S. A. Parameswaran
Author(s): Glenn Wagner, Yves H. Kwan, Nick Bultinck, Steven H. Simon, and S. A. Parameswaran

It is a matter of current debate whether the gate-tunable superconductivity in twisted bilayer graphene is phonon mediated or arises from electron-electron interactions. The recent observation of the strong coupling of electrons to so-called $K$-phonon modes in angle-resolved photoemission spectrosc…

[Phys. Rev. B 109, 104504] Published Wed Mar 13, 2024

Collective excitations in three-dimensional Dirac systems
Q. N. Li, P. Vasilopoulos, F. M. Peeters, W. Xu, Y. M. Xiao, and M. V. Milošević
Author(s): Q. N. Li, P. Vasilopoulos, F. M. Peeters, W. Xu, Y. M. Xiao, and M. V. Milošević

We provide the plasmon spectrum and related properties of the three-dimensional (3D) Dirac semimetals ${\mathrm{Na}}_{3}\mathrm{Bi}$ and ${\mathrm{Cd}}_{3}{\mathrm{As}}_{2}$ based on the random-phase approximation. The necessary one-electron eigenvalues and eigenfunctions are obtained from an effect…

[Phys. Rev. B 109, 115123] Published Wed Mar 13, 2024

Weyl nodal loop semimetals and tunable quantum anomalous Hall states in two-dimensional ferromagnetic cerium monohalides
Shu-Zong Li, Jun-Shan Si, Zhixiong Yang, and Wei-Bing Zhang
Author(s): Shu-Zong Li, Jun-Shan Si, Zhixiong Yang, and Wei-Bing Zhang

Quantum anomalous Hall (QAH) effect with dissipationless edge channels offers innovative insight for designing the next-generation low-power electronic devices. Based on first-principles calculations and the tight-binding (TB) model, we predict rich QAH states with a tunable Chern number in single-l…

[Phys. Rev. B 109, 115418] Published Wed Mar 13, 2024

Erratum: Edge channels in a graphene Fabry-Pérot interferometer [Phys. Rev. B 107, 235422 (2023)]
S. Ihnatsenka
Author(s): S. Ihnatsenka
[Phys. Rev. B 109, 119902] Published Wed Mar 13, 2024

Band mixing in the quantum anomalous Hall regime of twisted semiconductor bilayers
Ahmed Abouelkomsan, Aidan P. Reddy, Liang Fu, and Emil J. Bergholtz
Author(s): Ahmed Abouelkomsan, Aidan P. Reddy, Liang Fu, and Emil J. Bergholtz

Remarkable recent experiments have observed fractional quantum anomalous Hall effects at zero field and unusually high temperatures in twisted semiconductor bilayer $t{\mathrm{MoTe}}_{2}$, hence realizing the first genuine fractional Chern insulators. Intriguing observations in these experiments, su…

[Phys. Rev. B 109, L121107] Published Wed Mar 13, 2024

Self-energy corrections to zone-edge acoustic phonons in monolayer and bilayer ${\mathrm{WS}}_{2}$
Qixing Wang, Yu Li Huang, Qi Zhang, Jiayu Ma, Xin Luo, and Yun-Mei Li
Author(s): Qixing Wang, Yu Li Huang, Qi Zhang, Jiayu Ma, Xin Luo, and Yun-Mei Li

The self-energy corrections to phonons have mostly been observed for modes with zone-center ($q=0$) wave vectors. Here, we investigated the self-energy corrections to phonons in ionic-liquid-gated semiconductors, i.e., monolayer and bilayer ${\mathrm{WS}}_{2}$, experimentally. Apart from the previou…

[Phys. Rev. B 109, L121202] Published Wed Mar 13, 2024

Second-order topological states in a sixfold symmetric quasicrystal
Yuzhong Hu, Songmin Liu, Baoru Pan, Pan Zhou, and Lizhong Sun
Author(s): Yuzhong Hu, Songmin Liu, Baoru Pan, Pan Zhou, and Lizhong Sun

Recently, higher-order topology has been expanded to encompass aperiodic quasicrystals, including those with eightfold or twelvefold rotational symmetry. The underlying mechanism for these high-order topological phases is generally protected by ${C}_{n}{\mathcal{M}}_{z}$ symmetry, resulting in the p…

[Phys. Rev. B 109, L121403] Published Wed Mar 13, 2024

Found 1 papers in prx
Date of feed: Thu, 14 Mar 2024 04:17:09 GMT

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Spontaneous Gap Opening and Potential Excitonic States in an Ideal Dirac Semimetal ${\mathrm{Ta}}_{2}{\mathrm{Pd}}_{3}{\mathrm{Te}}_{5}$
Peng Zhang, Yuyang Dong, Dayu Yan, Bei Jiang, Tao Yang, Jun Li, Zhaopeng Guo, Yong Huang, Haobo, Qing Li, Yupeng Li, Kifu Kurokawa, Rui Wang, Yuefeng Nie, Makoto Hashimoto, Donghui Lu, Wen-He Jiao, Jie Shen, Tian Qian, Zhijun Wang, Youguo Shi, and Takeshi Kondo
Author(s): Peng Zhang, Yuyang Dong, Dayu Yan, Bei Jiang, Tao Yang, Jun Li, Zhaopeng Guo, Yong Huang, Haobo, Qing Li, Yupeng Li, Kifu Kurokawa, Rui Wang, Yuefeng Nie, Makoto Hashimoto, Donghui Lu, Wen-He Jiao, Jie Shen, Tian Qian, Zhijun Wang, Youguo Shi, and Takeshi Kondo

A new material hosts clean excitonic states—excitations of electron-hole pairs—thus providing a powerful platform for studying the novel physics of these excitations.

[Phys. Rev. X 14, 011047] Published Wed Mar 13, 2024

Found 1 papers in nano-lett
Date of feed: Wed, 13 Mar 2024 13:17:36 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] Engineering 2D Material Exciton Line Shape with Graphene/h-BN Encapsulation
Steffi Y. Woo, Fuhui Shao, Ashish Arora, Robert Schneider, Nianjheng Wu, Andrew J. Mayne, Ching-Hwa Ho, Mauro Och, Cecilia Mattevi, Antoine Reserbat-Plantey, Álvaro Moreno, Hanan Herzig Sheinfux, Kenji Watanabe, Takashi Taniguchi, Steffen Michaelis de Vasconcellos, Frank H. L. Koppens, Zhichuan Niu, Odile Stéphan, Mathieu Kociak, F. Javier García de Abajo, Rudolf Bratschitsch, Andrea Konečná, and Luiz H. G. Tizei

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Nano Letters
DOI: 10.1021/acs.nanolett.3c05063

Found 1 papers in acs-nano
Date of feed: Wed, 13 Mar 2024 13:12:20 GMT

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

[ASAP] Imaging Valley Excitons in a 2D Semiconductor with Scanning Tunneling Microscope-Induced Luminescence
Hairui Geng, Jie Tang, Yanwei Wu, Yuanqin Yu, Jeffrey R. Guest, and Rui Zhang

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ACS Nano
DOI: 10.1021/acsnano.3c12555

Found 1 papers in small
Date of feed: Wed, 13 Mar 2024 07:40:10 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)

The Nonvolatile Memory and Neuromorphic Simulation of ReS2/h‐BN/Graphene Floating Gate Devices Under Photoelectrical Hybrid Modulations
Wei Li, Jiaying Li, Tianhui Mu, Jiayao Li, Pengcheng Sun, Mingjian Dai, Yuhua Chen, Ruijing Yang, Zhao Chen, Yucheng Wang, Yupan Wu, Shaoxi Wang
Small, EarlyView.

Found 1 papers in adv-mater
Date of feed: Wed, 13 Mar 2024 07:29:50 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)

Engineering Anomalously Large Electron Transport in Topological Semimetals
Vincent M. Plisson, Xiaohan Yao, Yaxian Wang, George Varnavides, Alexey Suslov, David Graf, Eun Sang Choi, Hung‐Yu Yang, Yiping Wang, Marisa Romanelli, Grant McNamara, Birender Singh, Gregory T. McCandless, Julia Y. Chan, Prineha Narang, Fazel Tafti, Kenneth S. Burch
Advanced Materials, Accepted Article.