Found 58 papers in cond-mat
Date of feed: Tue, 17 Oct 2023 00:30:00 GMT

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Floquet-engineering the exceptional points in parity-time-symmetric magnonics. (arXiv:2310.09300v1 [cond-mat.mes-hall])
Xi-guang Wang, Lu-lu Zeng, Guang-hua Guo, Jamal Berakdar

Magnons serve as a testing ground for fundamental aspects of Hermitian and non-Hermitian wave mechanics and are of high relevance for information technology. This study presents setups for realizing spatio-temporally driven parity-time (PT) symmetric magnonics based on coupled magnetic waveguides and magnonic crystals. A charge current in a metal layer with strong spin-orbit coupling sandwiched between two insulating magnetic waveguides leads to gain or loss in the magnon amplitude depending on the directions of the magnetization and the charge currents. When gain in one waveguide is balanced by loss in the other waveguide a PT-symmetric system hosting non-Hermitian degeneracies (or exceptional points (EPs)) is realized. For AC current multiple EPs appear for a certain gain/loss strength and mark the boundaries between the preserved PT-symmetry and the broken PT-symmetry phases. The number of islands of broken PT-symmetry phases and their extensions is tunable by the frequency and the strength of the spacer current. At EP and beyond, the induced and amplified magnetization oscillations are strong and self-sustained. In particular, these magnetization auto-oscillations in broken PT-symmetry phase occur at low current densities and do not require further adjustments such as tilt angle between electric polarization and equilibrium magnetization direction in spin-torque oscillators, pointing to a new design of these oscillators and their utilization in computing and sensoric. It is also shown how the periodic gain/loss mechanism allows for the generation of high-frequency spin waves with low-frequency currents. For spatially-periodic gain/loss acting on a magnonic crystal, magnon modes approaching each other at the Brillouin-zone boundaries are highly susceptible to PT-symmetry, allowing for a wave-vector-resolved experimental realization at very low currents.

The interplay between exciton- and phonon-induced superconductivity might explain the phenomena observed in LK-99. (arXiv:2310.09305v1 [cond-mat.supr-con])
Junhui Cao, Alexey Kavokin

The experimental results hinting at the room temperature and ambient pressure superconductivity and magnetic levitation in LK-99 attracted an unprecedented interest. While attempts of other teams to reproduce the reported observations on similar samples failed so far, it seems worthwhile to try building a theoretical model that would explain the ensemble of the available data. One of important features that needs to be explained is an apparent contradiction between an extremely high critical temperature Tc and rather modest critical magnetic field Bc and critical current jc reported for LK-99. We show theoretically, that these data may be quantitatively reproduced assuming the interplay between exciton- and phonon-induced superconductivity, while the conventional BCS or Brinkman-Rice-Bardeen-Cooper-Schriefer (BR-BCS) mechanisms would result in a much higher Bc for the same Tc.

Weyl points and spin-orbit coupling in copper-substituted lead phosphate apatite. (arXiv:2310.09310v1 [cond-mat.mes-hall])
Martin Braß, Liang Si, Karten Held

We study the impact of spin-orbit coupling on the topological band-properties of copper-substituted lead phosphate apatite using a combination of group-theoretical analysis and full-relativistic density-functional theory calculations. We characterize Weyl points at time-reversal invariant momenta and find that a band-inversion due to spin-orbit coupling leads to additional Weyl points close to the Fermi-edge at general momenta. To determine the position of the altogether 66 Weyl points in the Brilouin-zone, we develop an algorithm that follows a Berry-curvature-derived vector field to its monopole: the Weyl point. The emerging surface Fermi-arcs and their spin-polarization reveal avoided crossings and a Fermi-loop detached from the Weyl points.

Accurate Kondo temperature determination of spin-1/2 magnetic impurities. (arXiv:2310.09326v1 [cond-mat.str-el])
Elia Turco, Markus Aapro, Somesh C. Ganguli, Nils Krane, Robert Drost, Nahual Sobrino, Annika Bernhardt, Michal Juríček, Roman Fasel, Pascal Ruffieux, Peter Liljeroth, David Jacob

At low temperatures, the interaction of a nanoscale magnet with a Fermi gas can give rise to the Kondo effect. This is signaled by a zero-bias resonance with a characteristic temperature evolution of its linewidth. In order to prove the Kondo nature of the zero-bias peak and to determine the Kondo temperature in scanning tunneling spectroscopy (STS), the extrinsic contributions to the measured linewidth have to be properly taken into account. In this paper, by combination of precise STS measurements of an ideal spin-1/2 Kondo system, phenalenyl on Au(111), and by theoretical considerations, we show how to efficiently extract accurate intrinsic Kondo linewidths from finite-temperature STS measurements. The extracted linewidths fit very well with a recently derived expression for the intrinsic Kondo linewidth as a function of temperature, thus proving the validity of the theory. Finally, we show that the developed methodology allows to reliably extract the intrinsic Kondo width from a single spectrum measured at finite temperature, thus considerably reducing the experimental effort.

Anomalous Hall effect in the antiferromagnetic Weyl semimetal SmAlSi. (arXiv:2310.09364v1 [cond-mat.mtrl-sci])
Yuxiang Gao, Shiming Lei, Eleanor M. Clements, Yichen Zhang, Xue-Jian Gao, Songxue Chi, Kam Tuen Law, Ming Yi, Jeffrey W. Lynn, Emilia Morosan

The intrinsic anomalous Hall effect (AHE) has been reported in numerous ferromagnetic (FM) Weyl semimetals. However, AHE in the antiferromagnetic (AFM) or paramagnetic (PM) state of Weyl semimetals has been rarely observed experimentally, and only in centrosymmetric materials. Different mechanisms have been proposed to establish the connection between the AHE and the type of magnetic order. In this paper, we report AHE in both the AFM and PM states of non-centrosymmetric compound SmAlSi. To account for the AHE in non-centrosymmetric Weyl semimetals without FM, we introduce a new mechanism based on magnetic field-induced Weyl nodes evolution. Angle-dependent quantum oscillations in SmAlSi provide evidence for the Weyl points and large AHE in both the PM and the AFM states. The proposed mechanism qualitatively explains the temperature dependence of the anomalous Hall conductivity (AHC), which displays unconventional power law behavior of the AHC in both AFM and PM states of SmAlSi.

Quantitative predictions of the thermal conductivity in transition metal dichalcogenides: The impact of point defects in MoS$_2$ and WS$_2$ monolayers. (arXiv:2310.09405v1 [cond-mat.mtrl-sci])
Srinivisan Mahendran, Jesús Carrete, Andreas Isacsson, Georg K. H. Madsen, Paul Erhart

Transition metal dichalcogenides are investigated for various applications at the nanoscale thanks to their unique combination of properties and dimensionality. For many of the anticipated applications, heat conduction plays an important role. At the same time, these materials often contain relatively large amounts of point defects. Here, we provide a systematic analysis of the impact of intrinsic and selected extrinsic defects on the lattice thermal conductivity of MoS$_2$ and WS$_2$ monolayers. We combine Boltzmann transport theory and the Green's function-based T-matrix approach for the calculation of scattering rates. The force constants for the defect configurations are obtained from density functional theory calculations via a regression approach, which allows us to sample a rather large number of defects at a moderate computational cost and to systematically enforce both the translational and rotational acoustic sum rules. The calculated lattice thermal conductivity is in quantitative agreement with experimental data for heat transport and defect concentrations for both MoS$_2$ and WS$_2$. Crucially, this demonstrates that the strong deviation from a 1/T-temperature dependence of the lattice thermal conductivity observed experimentally, can be fully explained by the presence of point defects. We furthermore predict the scattering strengths of the intrinsic defects to decrease in the sequence $V_{Mo}\approx V_{2S}^=>V_{2S}^\perp>V_S>S_{ad}$ in both materials, while the scattering rates for the extrinsic (adatom) defects decrease with increasing mass such that Li$_{ad}$>Na$_{ad}$>K$_{ad}$. Compared to earlier work, we find that both intrinsic and extrinsic adatoms are relatively weak scatterers. We attribute this difference to the treatment of the translational and rotational acoustic sum rules, which if not enforced can lead to spurious contributions in the zero-frequency limit.

Edge modes and symmetry-protected topological states in open quantum systems. (arXiv:2310.09406v1 [quant-ph])
Dawid Paszko, Dominic C. Rose, Marzena H. Szymańska, Arijeet Pal

Topological order offers possibilities for processing quantum information which can be immune to imperfections. However, the question of its stability out of equilibrium is relevant for experiments, where coupling to an environment is unavoidable. In this work we demonstrate the robustness of certain aspects of $Z_2 \times Z_2$ symmetry-protected topological (SPT) order against a wide class of dissipation channels in the Lindblad and quantum trajectory formalisms of an open quantum system. This is illustrated using the one-dimensional $ZXZ$ cluster Hamiltonian along with Pauli-string jump operators. We show that certain choices of dissipation retaining strong symmetries support a steady-state manifold consisting of two non-local logical qubits, and for Hamiltonian perturbations preserving the global symmetry, the manifold remains long-lived. In contrast, this metastability is destroyed upon breaking the above-mentioned symmetry. While the localized edge qubits of the cluster Hamiltonian are not conserved by the Lindbladian evolution, they do correspond to weak symmetries and thus retain a memory of their initial state at all times in the quantum trajectories. We utilize this feature to construct protocols to retrieve the quantum information either by monitoring jumps or error mitigation. Our work thus proposes a novel framework to study the dynamics of dissipative SPT phases and opens the possibility of engineering entangled states relevant to quantum information processing.

Topological properties of nearly flat bands in $\alpha-\mathcal{T}3$ lattice bilayer. (arXiv:2310.09415v1 [cond-mat.mtrl-sci])
Puspita Parui, Bheema Lingam Chittari

We study the effect of Haldane flux in bilayer $\alpha-\mathcal{T}_3$ lattice system for possible non-equivalent, commensurate stacking configurations with tight-binding formalism. Bilayer $\alpha-\mathcal{T}_3$ lattice has six sublattices in a unit cell and its spectrum comprises six bands.

In the absence of Haldane flux, there are threefold band-crossings at the two Dirac points for both valance and conduction bands. Introduction of Haldane flux in a cyclically stacked bilayer $\alpha-\mathcal{T}_3$ lattice system makes all six bands including two low-energy corrugated partial-flat bands separated and each band possesses non-zero Chern numbers, making the system topological.

It is shown that the topological evolution can be incorporated by modifying the hopping strength between sublattice $B$ and $C$ along all three directions, keeping those between $A$ and $B$ sublattices unchanged, or in other words, changing the parameter $\alpha$ in each layer.

In the dice lattice limit of the Chern-insulating phase, the Chern numbers of the three pairs of bands from low energy to higher energies are $\pm 2$, $\pm 3$, and $\pm 1$. Continuous change of parameter $\alpha$ invokes a phase transition through a band crossing between the two lower energy bands, at different values for conduction and valance bands, which further depend on the next nearest neighbor (NNN) hopping strength.

The Chern numbers of the two lower conduction and valance bands discontinuously change from $\pm2$ to $\pm 6$, $\pm 3$ to $0$ at the transition point, leaving the Chern number of the third band intact

Unveiling UV/IR Mixing via Symmetry Defects: A View from Topological Entanglement Entropy. (arXiv:2310.09425v1 [cond-mat.str-el])
Jintae Kim, Yun-Tak Oh, Daniel Bulmash, Jung Hoon Han

Some topological lattice models in two spatial dimensions have been found to exhibit intricate system size dependence in their ground state degeneracy (GSD), often known as UV/IR mixing. We distinguish between two explanations for this phenomenon by explicitly calculating the topological entanglement entropy (TEE) of a model system, the rank-2 toric code, for a bi-partition of the torus into two cylinders. Focusing on the fact that the rank-2 toric code is a translation symmetry-enriched topological phase, we show that viewing distinct system sizes as different translation symmetry defects can explain both our TEE results and the GSD of the rank-2 toric code. Our work establishes the symmetry defect framework as the most complete description of this system size dependence.

Coupled metamaterial-phonon terahertz range polaritons in a topological insulator. (arXiv:2310.09481v1 [cond-mat.mes-hall])
Sirak M. Mekonen, Deepti Jain, Seongshik Oh, N.P. Armitage

We report terahertz time-domain spectroscopy (TDTS) experiments demonstrating strong light-matter coupling in a terahertz (THz) LC-metamaterial in which the phonon resonance of a topological insulator (TI) thin film is coupled to the photonic modes of an array of electronic split-ring resonators. As we tune the metamaterial resonance frequency through the frequency of the low frequency $\alpha$ mode of (Bi$_x$Sb$_{1-x}$)$_2$Te$_3$ (BST), we observe strong mixing and level repulsion between phonon and metamaterial resonance. This hybrid resonance is a phonon polariton. We observe a normalized coupling strength, $\eta$ = $\Omega_R$/$\omega_c$ $\approx$ 0.09, using the measured vacuum Rabi frequency and cavity resonance. Our results demonstrate that one can tune the mechanical properties of materials by changing their electromagnetic environment and therefore modify their magnetic and topological degrees of freedom via coupling to the lattice in this fashion.

Effective electrical manipulation of topological antiferromagnet by orbital Hall effect. (arXiv:2310.09521v1 [cond-mat.mtrl-sci])
Zhenyi Zheng, Tao Zeng, Tieyang Zhao, Shu Shi, Lizhu Ren, Tongtong Zhang, Lanxin Jia, Youdi Gu, Rui Xiao, Hengan Zhou, Qihan Zhang, Jiaqi Lu, Guilei Wang, Chao Zhao, Huihui Li, Beng Kang Tay, Jingsheng Chen

Electrical control of the non-trivial topology in Weyl antiferromagnet is of great interests to develop next-generation spintronic devices. Recent works suggest that spin Hall effect can switch the topological antiferromagnetic order. However, the switching efficiency remains relatively low. Here, we demonstrate effective manipulation of antiferromagnetic order in Weyl semimetal Mn3Sn by orbital Hall effect originated from metal Mn or oxide CuOx. While Mn3Sn is proven to be able to convert orbit current to spin current by itself, we find that inserting a heavy metal layer like Pt with proper thickness can effectively reduce the critical switching current density by one order of magnitude. In addition, we show that the memristor-like switching behavior of Mn3Sn can mimic the potentiation and depression processes of a synapse with high linearity, which is beneficial for constructing artificial neural network with high accuracy. Our work paves an alternative way to manipulate topological antiferromagnetic order and may inspire more high-performance antiferromagnetic functional devices.

Chern numbers for the two-body Hofstadter-Hubbard butterfly. (arXiv:2310.09565v1 [cond-mat.quant-gas])
D. C. Alyuruk, M. Iskin

We analyze the two-body spectrum within the Hofstadter-Hubbard model on a square lattice through an exact variational ansatz and study the topological properties of its low-lying two-body bound-state branches. In particular we discuss how the Hofstadter-Hubbard butterfly of the two-body branches evolves as a function of onsite interactions and how to efficiently calculate their Chern numbers using the Fukui-Hatsugai-Suzuki approach. Our numerical results are fully consistent with the simple picture that appears in the strong-coupling limit, where the attraction between fermions forms a composite boson characterized by an effective hopping parameter and an effective magnetic-flux ratio.

Chiral magnetism, lattice dynamics, and anomalous Hall conductivity in the novel V$_3$AuN antiferromagnetic antiperovskite. (arXiv:2310.09616v1 [cond-mat.str-el])
J. M. Duran-Pinilla, Aldo H. Romero, A. C. Garcia-Castro

Antiferromagnetic antiperovskites, where magnetically active 3$d$ metal cations are placed in the octahedral corners of a perovskite structure, are in the spotlight due to their intertwined magnetic structure and topological properties. Especially their anomalous Hall conductivity, which can be controlled by applied strain and/or electric field, makes them highly attractive in different electronic applications. Here, we present the study and theoretical understanding of a new antiperovskite compound that can offer enormous opportunities in a broad set of applications. Using first-principles calculations, we investigated the structure, lattice dynamics, noncollinear magnetic ordering, and electronic behavior in the Vanadium-based antiperovskite V$_3$AuN. We found an antiperovskite structure centered on N similar to the Mn$_3A$N family as the structural ground state. In such a phase, a \emph{Pm$\bar{3}$m} ground state was found in contrast to the \emph{Cmcm} post-antiperovskite layered structure, as in the V$_3A$N, $A$ = Ga, Ge, As, and P. We studied the lattice dynamics and electronic properties, demonstrating its vibrational stability in the cubic structure and a chiral antiferromagnetic noncollinear ordering as a magnetic ground state. Finally, we found that the anomalous Hall conductivity, associated with the topological features induced by the magnetic symmetry, is $\sigma_{xy}$ = $-$291 S$\cdot$cm$^{-1}$ ($\sigma_{111}$ = $-$504 S$\cdot$cm$^{-1}$). The latter is the largest reported in the antiferromagnetic antiperovskite family of compounds.

Moir\'e excitons in biased twisted bilayer graphene under pressure. (arXiv:2310.09645v1 [cond-mat.mes-hall])
V. G. M. Duarte, D. R. da Costa, N. M. R. Peres, L. K. Teles, A. J. Chaves

Using the tight-binding model, we report a gap opening in the energy spectrum of the twisted bilayer graphene under the application of pressure, that can be further amplified by the presence of a perpendicular bias voltage. The valley edges are located along the K-Gamma path of the superlattice Brillouin Zone, with the bandgap reaching values up to 200 meV in the single-particle picture. Employing the formalism of the semiconductor Bloch equations, we observe an enhancement of the bandgap due to the electron-electron interaction, with a renormalization of the bandgap of about 160 meV. From the solution of the corresponding Bethe-Salpeter equation, we show that this system supports highly anisotropic bright excitons whose electrons and holes are strongly hybridized between the adjacent layers.

Excitonic effects in nonlinear optical responses: Exciton-state formalism and first-principles calculations. (arXiv:2310.09674v1 [cond-mat.mtrl-sci])
Jiawei Ruan, Y.-H. Chan, Steven G. Louie

Nonlinear optical (NLO) responses have garnered tremendous interest for decades due to their fundamental and technological interests. The theory and calculations of NLO responses including electron-hole interactions, which is especially crucial for reduced-dimensional materials, however, remain underdeveloped. Here, we develop an ab initio approach to calculate second-order nonlinear responses (such as second harmonic generation (SHG) and shift current) with excitonic effects in an exciton-state basis, going beyond the independent-particle approximation. We compute SHG in monolayer h-BN and MoS2 employing exciton states from GW-Bethe-Salpeter equation (GW-BSE) calculations and show both materials exhibit huge excitonic enhancement. The physical origin of the enhancement is directly understood through the coupling amplitudes among exciton states, assisted with diagrammatic representations. Our method provides an accurate and ab initio description of second-order NLO responses, capturing self-energy and electron-hole interaction effects.

A singlet-triplet hole-spin qubit in MOS silicon. (arXiv:2310.09722v1 [cond-mat.mes-hall])
S. D. Liles, D. J. Halverson, Z. Wang, A. Shamim, R. S. Eggli, I. K. Jin, J. Hillier, K. Kumar, I. Vorreiter, M. Rendell, J. H. Huang, C. C. Escott, F. E. Hudson, W. H. Lim, D. Culcer, A. S. Dzurak, A. R. Hamilton

Holes in silicon quantum dots are promising for spin qubit applications due to the strong intrinsic spin-orbit coupling. The spin-orbit coupling produces complex hole-spin dynamics, providing opportunities to further optimize spin qubits. Here, we demonstrate a singlet-triplet qubit using hole states in a planar metal-oxide-semiconductor double quantum dot. We observe rapid qubit control with singlet-triplet oscillations up to 400 MHz. The qubit exhibits promising coherence, with a maximum dephasing time of 600 ns, which is enhanced to 1.3 us using refocusing techniques. We investigate the magnetic field anisotropy of the eigenstates, and determine a magnetic field orientation to improve the qubit initialisation fidelity. These results present a step forward for spin qubit technology, by implementing a high quality singlet-triplet hole-spin qubit in planar architecture suitable for scaling up to 2D arrays of coupled qubits.

Phase- and angle-sensitive terahertz hot-electron bolometric plasmonic detectors based on FETs with graphene channel and composite h-BN/black-P/h-BN gate layer. (arXiv:2310.09741v1 [cond-mat.mes-hall])
V. Ryzhii, M. S. Shur, M. Ryzhii, V. Mitin, C. Tang, T. Otsuji

We propose and analyze the terahertz (THz) bolometric vector detectors based on the graphene-channel field-effect transistors (GC-FET) with the black-P gate barrier layer or with the composite b-BN/black-P/b-BN gate layer. The phase difference between the signal received by the FET source and drain substantially affects the plasmonic resonances. This results in a resonant variation of the detector response on the incoming THz signal phase shift and the THz radiation angle of incidence.

Topological Properties of Single-Particle States Decaying into a Continuum due to Interaction. (arXiv:2310.09957v1 [cond-mat.mes-hall])
B. Hawashin, J. Sirker, G. S. Uhrig

We investigate how topological Chern numbers can be defined when single-particle states hybridize with continua. We do so exemplarily in a bosonic Haldane model at zero temperature modified by an additional on-site decay of one boson into two and the conjugate fusion of two bosons into one. Restricting the Hilbert space to two bosons at maximum, the exact self-energy is accessible. We use the bilinear Hamiltonian $H_0$ corrected by the self-energy $\Sigma$ to compute Chern numbers by two different approaches. The results are gauged against a full many-body calculation in the restricted Hilbert space. We find evidence that the effective Hamiltonian $H_0(\vec k) +\Sigma(\omega,\vec k)$ reproduces the correct many-body topology even if the considered band overlaps with the continuum. However, in the latter case the bulk-boundary correspondence appears to be no longer valid and the edge modes delocalize.

Defect-induced helicity-dependent terahertz emission in Dirac semimetal PtTe2 thin films. (arXiv:2310.09989v1 [cond-mat.mtrl-sci])
Zhongqiang Chen, Hongsong Qiu, Xinjuan Cheng, Jizhe Cui, Zuanming Jin, Da Tian, Ruxin Liu, Xu Zhang, Wei Niu, Liqi Zhou, Tianyu Qiu, Zhe Wang, Yequan Chen, Caihong Zhang, Xiaoxiang Xi, Fengqi Song, Rong Yu, Xuechao Zhai, Biaobing Jin, Rong Zhang, Xuefeng Wang

Nonlinear transport enabled by symmetry breaking in quantum materials has aroused considerable interests in condensed matter physics and interdisciplinary electronics. However, the nonlinear optical response in centrosymmetric Dirac semimetals via the defect engineering has remained extremely challenging. Here, we observe the helicity-dependent terahertz (THz) emission in Dirac semimetal PtTe2 thin films via circular photogalvanic effect (CPGE) under normal incidence. This is activated by artificially controllable Te-vacancy defect gradient, which is unambiguously evidenced by the electron ptychography. The defect gradient lowers the symmetry, which not only induces the band spin splitting, but also generates the Berry curvature dipole (BCD) responsible for the CPGE. Such BCD-induced helicity-dependent THz emission can be manipulated by the Te-vacancy defect concentration. Furthermore, temperature evolution of the THz emission features the minimum of the THz amplitude due to the carrier compensation. Our work provides a universal strategy for symmetry breaking in centrosymmetric Dirac materials for nonlinear transport and facilitates the promising device applications in integrated optoelectronics and spintronics.

Variations of Interatomic Force Constants in the Topological Phonon Phase Transition of AlGaN. (arXiv:2310.09996v1 [cond-mat.mtrl-sci])
Daosheng Tang

The topological effects of phonons have been extensively studied in various materials, particularly in the wide-bandgap semiconductor GaN, which has the potential to improve heat dissipation in power electronics due to its intrinsic, topologically-protected, non-dissipative phonon surface states. Nevertheless, the phase transition of the Weyl phonons in nitrides and their composite alloys has yet to be elucidated. To unveil the microscale origin, topological phonon properties in AlGaN alloys are investigated using the virtual crystal approximation (VCA) and special quasi-random structure (SQS) approaches in this work. It is found that phase transitions in Weyl phonons are evidently present in AlGaN alloys and nitride single crystals. Under strain states, both GaN and AlN show a more prominent phase transition of Weyl phonons when subjected to biaxial compressive and uniaxial tensile strains. And it has been observed that the zz components in the self-term and the transverse 1NN force constants (FCs) are the most influential during the phase transition. The nonlinear Weyl phonon transition in AlGaN alloys, as modeled by the VCA, is reflected in the normalized self-term and first-nearest-neighbor (1NN) FCs, which vary in a nonlinear fashion with an increasing magnitude. This nonlinear phenomenon is also confirmed in the SQS modeling, where the unfolded phonon dispersions are consistent with those in the VCA modeling. With increased branches, hundreds of Weyl phonons are present accompanied by significant disorders in normalized FCs, which mainly occur for N atoms in self-terms and for all components in normalized 1NN FCs.

Optimized nanodevice fabrication using clean transfer of graphene by polymer mixture: Experiments and Neural Network based simulations. (arXiv:2310.10020v1 [])
Jared K. Averitt, Sajedeh Pourianejad, Olubunmi Ayodele, Kirby Schmidt, Anthony Trofe, Joseph Starobin, Tetyana Ignatova

In this study, we investigate both experimentally and computationally the molecular interactions of two distinct polymers with graphene. Our experimental findings indicate that the use of a polymer mixture reduces the transfer induced doping and strain in fabricated graphene devices as compared to conventional single polymer wet transfer. We found that such reduction is related to the decreased affinity of mixture of polymethyl methacrylate and angelica lactone polymer for graphene. We investigated changes in binding energy (BE) of polymer mixture and graphene by considering energy decomposition analysis using a pre-trained potential neural network. It was found that numerical simulations accurately predicted two-fold reduction of BE and order of magnitude reduction of electrostatic interaction between polymers.

Magnetic response of a two-dimensional viscous electron fluid. (arXiv:2310.10032v1 [cond-mat.mes-hall])
Aydin Cem Keser, Oleg Sushkov

It has been established that the Coulomb interactions can transform the electron gas into a viscous fluid. This fluid is realized in a number of platforms, including graphene and two-dimensional semiconductor heterostructures. The defining characteristic of the electron fluid is the formation of layers of charge carriers that are in local thermodynamic equilibrium, as in classical fluids. In the presence of nonuniformities, whirlpools and nontrivial flow profiles are formed, which have been directly imaged in recent experiments. In this paper, we theoretically study the response of the electron fluid to localized magnetic fields. We find that the electric current is suppressed by viscous vortices in regions where magnetic field is sharply varying, causing strong transport signatures. Experimentally, our considerations are relevant since local magnetic fields can be applied to the system through implanting adatoms or embedding micromagnets in the top-gate. Our theory is essential for the characterization and future applications of electron fluids in hydrodynamic spin transport.

Emergent spin-gapped magnetization plateaus in a spin-1/2 perfect kagome antiferromagnet. (arXiv:2310.10069v1 [cond-mat.str-el])
S. Suetsugu, T. Asaba, Y. Kasahara, Y. Kohsaka, K. Totsuka, B. Li, Y. Zhao, Y. Li, M. Tokunaga, Y. Matsuda

The two-dimensional (2D) spin-1/2 kagome Heisenberg antiferromagnet is believed to host quantum spin liquid (QSL) states with no magnetic order, but its ground state remains largely elusive. An important outstanding question concerns the presence or absence of the 1/9 magnetization plateau, where exotic quantum states, including topological ones, are expected to emerge. Here we report the magnetization of a recently discovered kagome QSL candidate YCu$_3$(OH)$_{6.5}$Br$_{2.5}$ up to 57 T. Above 50 T, a clear magnetization plateau at 1/3 of the saturation moment of Cu$^{2+}$ ions is observed, supporting that this material provides an ideal platform for the kagome Heisenberg antiferromagnet. Remarkably, we found another magnetization plateau around 20 T, which is attributed to the 1/9 plateau. The temperature dependence of this plateau reveals the distinct spin gap, whose magnitude estimated by the plateau width is approximately 10% of the exchange interaction. The observation of 1/9 and 1/3 plateaus highlights the emergence of novel states in quantum spin systems.

Growth and characterization of the magnetic topological insulator candidate Mn$_2$Sb$_2$Te$_5$. (arXiv:2310.10163v1 [cond-mat.mtrl-sci])
Ankush Saxena, V.P.S. Awana (CSIR-NPL, India)

We report a new member of topological insulator (TI) family i.e., Mn$_2$Sb$_2$Te$_5$, which belongs to MnSb$_2$Te$_4$ family and is a sister compound of Mn$_2$Bi$_2$Te$_5$. An antiferromagnetic layer of (MnTe)$_2$ has been inserted between quintuple layers of Sb$_2$Te$_3$. The crystal structure and chemical composition of as grown Mn$_2$Sb$_2$Te$_5$ crystal is experimentally visualized by single crystal XRD (SCXRD) and field emission scanning electron microscopy (FESEM). The valence states of individual constituents i.e., Mn, Sb and Te are ascertained through X ray photo electron spectroscopy (XPS). Different vibrational modes of Mn$_2$Sb$_2$Te$_5$ are elucidated through Raman spectroscopy. Temperature-dependent resistivity of Mn$_2$Sb$_2$Te$_5$ resulted in metallic behaviour of the same with an up-turn at below around 20K. Further, the magneto-transport R(T) vs H of the same exhibited negative magneto-resistance (MR) at low temperatures below 20K and small positive at higher temperatures. The low Temperature -ve MR starts decreasing at higher fields. The magnetic moment as a function of temperature at 100Oe and 1kOe showed AFM like down turn cusps at around 20K and 10K. The isothermal magnetization (MH) showed AFM like loops with some embedded FM/PM domains at 5K and purely paramagnetic (PM) like at 100K. The studied Mn$_2$Sb$_2$Te$_5$ clearly exhibited the characteristics of a magnetic TI (MTI).

Optical properties of anisotropic Dirac semimetals. (arXiv:2310.10172v1 [cond-mat.mes-hall])
I. Kupčić, J. Kordić

The current-dipole conductivity formula for doped three-dimensional Dirac semimetals is derived by using a modified gauge-invariant tight-binding approach. In a heavily doped regime, the effective number of charge carriers $n_{\alpha \alpha}^{\rm eff}$ in the Drude contribution is found to be by a factor of 4 larger than the nominal electron concentration $n$. However, its structure is the same as in standard Fermi liquid theory. In a lightly doped regime, on the other hand, the ratio $n_{\alpha \alpha}^{\rm eff}/n$ is much larger, with much more complex structure of $n_{\alpha \alpha}^{\rm eff}$. It is shown that the dc resistivity and reflectivity date measured in two TlBiSSe samples can be easily understood, even in the relaxation-time approximation, provided that finite quasiparticle lifetime effects in the momentum distribution functions are properly taken into account.

A proposal for realizing Majorana fermions without magnetic field in strongly correlated nanowires. (arXiv:2310.10201v1 [cond-mat.supr-con])
Kaushal Kumar Kesharpu, Evgenii A. Kochetov, Alvaro Ferraz

We show that one dimensional (1D) topological superconductivity can be placed in the context of phenomena associated with strongly correlated electron systems. Here we propose a system consisting of a one-dimensional chain of strongly correlated fermions placed on a superconducting (SC) substrate that exhibits a spin-singlet extended $s$-wave pairing. Strong electron correlation is shown to transform an extended $s$-wave SC into a topological SC that hosts Majorana fermions. In contrast to the approaches based on mean-field treatments, no Zeeman or exchange magnetic field is needed to produce such an effect.

Majorana Fermion Mean-Field Theories of Kitaev Quantum Spin Liquids. (arXiv:2310.10230v1 [cond-mat.str-el])
Shahnam Ghanbari Saheli, Jennifer Lin, Huanzhi Hu, Frank Krüger

We determine the phase diagrams of anisotropic Kitaev-Heisenberg models on the honeycomb lattice using parton mean-field theories based on different Majorana fermion representations of the $S=1/2$ spin operators. Firstly, we use a two-dimensional Jordan-Wigner transformation (JWT) involving a semi-infinite snake string operator. In order to ensure that the fermionized Hamiltonian remains local we consider the limit of extreme Ising exchange anisotropy in the Heisenberg sector. Secondly, we use the conventional Kitaev representation in terms of four Majorana fermions subject to local constraints, which we enforce through Lagrange multipliers. For both representations we self-consistently decouple the interaction terms in the bond and magnetization channels and determine the phase diagrams as a function of the anisotropy of the Kitaev couplings and the relative strength of the Ising exchange. While both mean-field theories produce identical phase boundaries for the topological phase transition between the gapless and gapped Kitaev quantum spin liquids, the JWT fails to correctly describe the the magnetic instability and finite-temperature behavior. Our results show that the magnetic phase transition is first order at low temperatures but becomes continuous above a certain temperature.

Optical switching beyond a million cycles of low-loss phase change material Sb$_2$Se$_3$. (arXiv:2310.10252v1 [physics.optics])
Daniel Lawson, Sophie Blundell, Martin Ebert, Otto L. Muskens, Ioannis Zeimpekis

The development of the next generation of optical phase change technologies for integrated photonic and free-space platforms relies on the availability of materials that can be switched repeatedly over large volumes and with low optical losses. In recent years, the antimony-based chalcogenide phase-change material Sb$_2$Se$_3$ has been identified as particularly promising for a number of applications owing to good optical transparency in the near-infrared part of the spectrum and a high refractive index close to silicon. The crystallization temperature of Sb$_2$Se$_3$ of around 460 K allows switching to be achieved at moderate energies using optical or electrical control signals while providing sufficient data retention time for non-volatile storage. Here, we investigate the parameter space for optical switching of films of Sb$_2$Se$_3$ for a range of film thicknesses relevant for optical applications. By identifying optimal switching conditions, we demonstrate endurance of up to 10$^7$ cycles at reversible switching rates of 20 kHz. Our work demonstrates that the combination of intrinsic film parameters with pumping conditions is particularly critical for achieving high endurance in optical phase change applications.

In-Situ Single Particle Reconstruction Reveals 3D Evolution of PtNi Nanocatalysts During Heating. (arXiv:2310.10253v1 [])
Yi-Chi Wang, Thomas J A Slater, Gerard M. Leteba, Candace I Lang, Zhong Lin Wang, Sarah J Haigh

Tailoring nanoparticles composition and morphology is of particular interest for improving their performance for catalysis. A challenge of this approach is that the nanoparticles optimized initial structure often changes during use. Visualizing the three dimensional (3D) structural transformation in situ is therefore critical, but often prohibitively difficult experimentally. Although electron tomography provides opportunities for 3D imaging, restrictions in the tilt range of in situ holders together with electron dose considerations limit the possibilities for in situ electron tomography studies. Here, we present an in situ 3D imaging methodology using single particle reconstruction (SPR) that allows 3D reconstruction of nanoparticles with controlled electron dose and without tilting the microscope stage. This in situ SPR methodology was employed to investigate the restructuring and elemental redistribution within a population of PtNi nanoparticles at elevated temperatures. We further examined the atomic structure of PtNi and found a heat induced transition from a disordered to an ordered phase. Changes in structure and elemental distribution were linked to a loss of catalytic activity in the oxygen reduction reaction. The in situ SPR methodology employed here could be extended to a wide range of in situ studies employing not only heating, but gaseous, aqueous or electrochemical environments to reveal in operando nanoparticle evolution in 3D.

Topological phases of monolayer and bilayer depleted Lieb lattices. (arXiv:2310.10286v1 [cond-mat.mes-hall])
Arghya Sil, Asim Kumar Ghosh

Existence of nontrivial topological phases in a tight binding Haldane-like model on the depleted Lieb lattice is reported. This two-band model is formulated by considering the nearest-neighbor, next-nearest-neighbor and next-next-nearest-neighbor hopping terms along with complex phase which breaks the time reversal symmetry of this semi-metallic system. Topological feature of this model is studied along with the presence of sublattice symmetry breaking staggered onsite energy. Combined effect of these two broken symmetries is found crucial for an additional transition between nontrivial and trivial phases. System exhibits two types of phase transitions, say, between two nontrivial phases and nontrivial to trivial phases. Nonzero Chern numbers, existence of Hall plateau and symmetry protected edge states confirm the presence of the nontrivial phases. This two-band system hosts four different types of phases where two are topological. Additionally topological properties of stacked bilayer of the depleted Lieb lattices is also studied with similar Haldane-like Hamiltonian. This four-band system is found to host Chern insulating phases, with higher values of Chern numbers supported by in-gap edge states.

Tunneling density of states of fractional quantum Hall edges: an unconventional bosonization approach. (arXiv:2310.10319v1 [cond-mat.mes-hall])
Nikhil Danny Babu, Girish S. Setlur

An unconventional bosonization approach that employs a modified Fermi-Bose correspondence is used to obtain the tunneling density of states (TDOS) of fractional quantum Hall (FQHE) edges in the vicinity of a point contact. The chiral Luttinger liquid model is generally used to describe FQHE edge excitations. We introduce a bosonization procedure to study edge state transport in Laughlin states at filling $\nu = 1/m$ with $m$ odd (single edge mode) in the presence of a point contact constriction that brings the top and bottom edges of the sample into close proximity. The unconventional bosonization involves modifying the Fermi-Bose correspondence to incorporate backscattering at the point contact, leaving the action of the theory purely quadratic even in presence of the inhomogeneity. We have shown convincingly in earlier works that this procedure correctly reproduces the most singular parts of the Green functions of the system even when mutual forward scattering between fermions are included. The most singular part of the density-density correlation function (DDCF) relevant to TDOS calculation is computed using a generating functional approach. The TDOS for both the electron tunneling as well as the Laughlin quasiparticle tunneling cases is obtained and is found to agree with previous results in the literature. For electron tunneling the well-known universal power laws for TDOS viz. $ \sim \mbox{ }\omega^{ m-1 }$ and for quasi-particle tunneling the power law $ \sim \mbox{ } \omega^{ \frac{1}{m}-1 } $ are both correctly recovered using our unconventional bosonization scheme. This demonstrates convincingly the utility of the present method which unlike conventional approaches, does not treat the point-contact as an afterthought and yet remains solvable so long as only the most singular parts of the correlation functions are desired.

Axionic Instability of Periodic Weyl-Semimetal Superstructures. (arXiv:2310.10345v1 [cond-mat.mes-hall])
Tommy Li, Maxim Breitkreiz

Weyl-semimetal superstructures with a spiraling position of a pair of Weyl nodes of opposite chirality can host a chiral-symmetry preserving Fermi-arc metal state, where the chirality is carried by cylindrical Fermi surfaces, electron- and hole-like depending on the chirality. The Fermi surfaces nest at vanishing momentum separation (zero nesting vector) at the electron-hole-compensation energy because the nesting is topologically protected by vanishing spatial overlap of any pair of equal-momentum opposite-chirality states. In this work we show that the nesting and Coulomb interaction drive a spontaneous chiral symmetry breaking in such a Fermi arc metal, which leads to a dynamical axion insulator state but without breaking translational symmetry (no charge-density-wave order) as in a conventional Weyl semimetal. As for material realization, we discuss magnetically doped Bi$_2$Se$_3$, for which the Weyl-node positions depend on the order of the magnetic dopands. In this case, the axionic condensation can itself stabilize a spiral order of the magnetization, and hence the spiraling node positions, even if the magnetic interaction is intrinsically ferromagnetic.

Berry Curvature and Bulk-Boundary Correspondence from Transport Measurement for Photonic Chern Bands. (arXiv:2310.10365v1 [quant-ph])
Chao Chen, Run-Ze Liu, Jizhou Wu, Zu-En Su, Xing Ding, Jian Qin, Lin Wang, Wei-Wei Zhang, Yu He, Xi-Lin Wang, Chao-Yang Lu, Li Li, Barry C. Sanders, Xiong-Jun Liu, Jian-Wei Pan

Berry curvature is a fundamental element to characterize topological quantum physics, while a full measurement of Berry curvature in momentum space was not reported for topological states. Here we achieve two-dimensional Berry curvature reconstruction in a photonic quantum anomalous Hall system via Hall transport measurement of a momentum-resolved wave packet. Integrating measured Berry curvature over the two-dimensional Brillouin zone, we obtain Chern numbers corresponding to -1 and 0. Further, we identify bulk-boundary correspondence by measuring topology-linked chiral edge states at the boundary. The full topological characterization of photonic Chern bands from Berry curvature, Chern number, and edge transport measurements enables our photonic system to serve as a versatile platform for further in-depth study of novel topological physics.

A mono-atomic orbital-based 1D topological crystalline insulator. (arXiv:2310.10403v1 [cond-mat.mes-hall])
Gengming Liu, Violet Workman, Jiho Noh, Yuhao Ma, Taylor L. Hughes, Wladimir A. Benalcazar, Gaurav Bahl

Topological crystalline insulators (TCIs) are classified by topological invariants defined with respect to the crystalline symmetries of their gapped bulk. The bulk-boundary correspondence then links the topological properties of the bulk to robust observables on the edges, e.g., the existence of robust edge modes or fractional charge. In one dimension, TCIs protected by reflection symmetry have been realized in a variety of systems where each unit cell has spatially distributed degrees of freedom (SDoF). However, these realizations of TCIs face practical challenges stemming from the sensitivity of the resulting edge modes to variations in edge termination and to the local breaking of the protective spatial symmetries by inhomogeneity. Here we demonstrate topologically protected edge states in a mono-atomic, orbital-based TCI that mitigates both of these issues. By collapsing all SDoF within the unit cell to a singular point in space, we eliminate the ambiguity in unit cell definition and hence remove a prominent source of boundary termination variability. The topological observables are also more tolerant to disorder in the orbital energies. To validate this concept, we experimentally realize a lattice of mechanical resonators where each resonator acts as an "atom" that harbors two key orbital degrees of freedom having opposite reflection parity. Our measurements of this system provide direct visualization of the $sp$-hybridization between orbital modes that leads to a non-trivial band inversion in the bulk. Furthermore, as the spatial width of the resonators is tuned, one can drive a transition between a topological and trivial phase. In the future we expect our approach can be extended to realize orbital-based obstructed atomic insulators and TCIs in higher dimensions.

Spin Splitting and Disorder in HgTe-Based Massless Dirac Fermion Landau Levels. (arXiv:2310.10473v1 [cond-mat.mes-hall])
D. A. Kozlov, J. Ziegler, N. N. Mikhailov, Z. D. Kvon, D.Weiss

An experimental study of Landau levels (LLs) in a system of two-dimensional massless Dirac fermions based on a critical thickness HgTe quantum well has been carried out. The magnetotransport and the capacitive response have been investigated simultaneously. It is shown that the formation of Shubnikov-de Haas (SdH) oscillations associated with odd v filling factors occurs in a magnetic field whose strength grows monotonically with v. This behavior is consistent with calculations of the electron spectrum, which predicts a decrease in cyclotron gaps with increasing v. Oscillations with even filling factors, corresponding to spin gaps, behave less trivially. First, the SdH oscillations with filling factors of 4 and higher are resolved in a magnetic field that is 2-2.5 times smaller than the field required to resolve neighboring SdH oscillations with odd filling factors of 3 and higher. This indicates a significant increase in the size of the spin gap caused by an interface inversion asymmetry (IIA) leading to Dirac cone splitting in a zero magnetic field. Using the spin splitting value gamma as a fitting parameter, we obtained the best agreement between experimental data and calculations at gamma=1.5 meV. Next, spin splitting for the zeroth and first LLs is observed in 2-3 times stronger magnetic fields than for the other levels, indicating an increase in disorder near the Dirac point, due to the lack of screening.

Metastable phase of UTe$_2$ formed under high pressure above 5 GPa. (arXiv:2310.10491v1 [cond-mat.str-el])
L. Q. Huston, D. Y. Popov, A. Weiland, M. M. Bordelon, P. F. S. Rosa, R. L. Rowland II, B. L. Scott, G. Shen, C. Park, E. K. Moss, S. M. Thomas, J. D. Thompson, B. T. Sturtevant, E. D. Bauer

Uranium ditelluride (UTe$_2$) has attracted recent interest due to its unique superconducting properties, which include the potential for a topological odd-parity superconducting state. Recently, ac-calorimetry measurements under pressure indicate a change in the ground state of UTe$_2$ from superconducting to antiferromagnetic at 1.4 GPa. Here, we investigate the effect of pressure on the crystal structure of UTe$_2$ up to 25 GPa at room temperature using x-ray diffraction. We find that UTe$_2$, which at ambient conditions has an orthorhombic ($Immm$) structure, transforms to a body-centered tetragonal ($I4/mmm$) structure at 5 GPa in a quasi-hydrostatic neon (Ne) pressure transmitting medium. In the absence of a pressure-transmitting medium, this transformation occurs between 5 and 8 GPa. The data were fit with a third-order Birch-Murnaghan equation of state resulting in values of $B_0$=46.0 $\pm$ 0.6 GPa, $B^{\prime}$=9.3 $\pm$ 0.5 (no pressure medium) and $B_0$=42.5 $\pm$ 2.0 GPa, $B^{\prime}$=9.3 (fixed) (neon pressure medium) for the $Immm$ phase. For the $I4/mmm$ phase, $B_0$=78.9 $\pm$ 0.5 GPa and $B^{\prime}$=4.2 $\pm$ 0.1 (no pressure transmitting medium), and $B_0$=70.0 $\pm$ 1.1 GPa and $B^{\prime}$=4.1 $\pm$ 0.2 (neon pressure medium). The high-pressure tetragonal phase is retained after decompression to ambient pressure, with approximately 30% remaining after 2 days. We argue that the observed phase transition into a higher symmetry structure at P~5 GPa (orthorhombic to tetragonal), is accompanied by an increase in the shortest distance between uranium atoms from 3.6 Angstrom (orthorhombic) to 3.9 Angstrom (tetragonal), which suggests localization of the 5f electrons, albeit with a 10.7% decrease in volume.

Quantum Transport of Charge Density Wave Electrons in Layered Materials. (arXiv:2310.10512v1 [cond-mat.mes-hall])
John H. Miller Jr, Martha Y. Suárez-Villagrán, Johnathan O. Sanderson

The charge density wave (CDW) is a condensate that often forms in layered materials. It is known to carry electric current \emph{en masse}, but the transport mechanism remains poorly understood at the microscopic level. Its quantum nature is revealed by several lines of evidence. Experiments often show lack of CDW displacement when biased just below the threshold for nonlinear transport, indicating the CDW never reaches the critical point for classical depinning. Quantum behavior is also revealed by oscillations of period $h/2e$ in CDW conductance vs. magnetic flux, sometimes accompanied by telegraph-like switching, in $\text{TaS}_3$ rings above 77 K. Here we discuss further evidence for quantum CDW electron transport. We find that, for temperatures ranging from 9 to 474 K, CDW current-voltage plots of three trichalcogenide materials agree almost precisely with a modified Zener-tunneling curve and with time-correlated soliton tunneling model simulations. In our model we treat the Schr\"{o}dinger equation as an emergent classical equation that describes fluidic Josephson-like coupling of paired electrons between evolving topological states. We find that an extension of this \lq classically robust' quantum picture explains both the $h/2e$ magnetoconductance oscillations and switching behavior in CDW rings. We consider potential applications for thermally robust quantum information processing systems.

Doping-Induced Electronic and Structural Phase Transition in the Bulk Weyl Semimetal Mo1-xWxTe2. (arXiv:2310.10593v1 [cond-mat.mtrl-sci])
O. Fedchenko, F. K. Diekmann, P. Russmann, M. Kallmayer, L. Odenbreit, S. M. Souliou, M. Frachet, A. Winkelmann, M. Merz, S. V. Chernov, D. Vasilyev, D. Kutnyakhov, O. Tkach, Y. Lytvynenko, K. Medjanik, C. Schlueter, A. Gloskovskii, T. R. F. Peixoto, M. Hoesch, M. Le Tacon, Y. Mokrousov, K. Rossnage, G. Schönhense, H.-J. Elmers

A comprehensive study of the electronic and structural phase transition from 1T` to Td in the bulk Weyl semimetal Mo1-xWxTe2 at different doping concentrations has been carried out using time-of-flight momentum microscopy (including circular and linear dichroism), X-ray photoelectron spectroscopy (XPS), X-ray photoelectron diffraction (XPD), X-ray diffraction (XRD), angle-resolved Raman spectroscopy, transport measurements, density functional theory (DFT) and Kikuchi pattern calculations. High-resolution angle-resolved photoemission spectroscopy (ARPES) at 20 K reveals surface electronic states, which are indicative of topological Fermi arcs. Their dispersion agrees with the position of Weyl points predicted by DFT calculations based on the experimental crystal structure of our samples determined by XRD. Raman spectroscopy confirms the inversion symmetry breaking for the Td -phase, which is a necessary condition for the emergence of topological states. Transport measurements show that increasing the doping concentration from 2 to 9% leads to an increase in the temperature of the phase transition from 1T` to Td from 230 K to 270 K. Magnetoresistance and longitudinal elastoresistance show significantly increased values in the Td -phase due to stimulated inter-pocket electron backscattering. The results demonstrate the close relationship between electronic properties and elastic deformations in MoTe2.

Nonequilibrium dynamics in Dirac quantum criticality. (arXiv:2310.10601v1 [cond-mat.str-el])
Yin-Kai Yu, Zhi Zeng, Yu-Rong Shu, Zi-Xiang Li, Shuai Yin

Quantum criticality within Dirac fermions harbors a plethora of exotic phenomena, attracting sustained attention in the past decades. Nevertheless, the nonequilibrium dynamics therein has rarely been studied. To fill in the gap, we explore the imaginary-time relaxation dynamics in a typical Dirac quantum criticality belonging to chiral Heisenberg universality class. Performing large-scale quantum Monte Carlo simulation, we unveil rich nonequilibrium critical phenomena from different initial states. Particularly, a new dynamic exponent characterizing the non-stationary evolution in the short-time state is determined as $\theta=-0.84(4)$, in sharp contrast with the prevalent belief that $\theta$ is positive as demonstrated in classical cases. Furthermore, we propose a universal dynamic scaling theory governing the fruitful nonequilibrium properties in Dirac quantum criticality. Armed with the scaling theory, we develop a new framework to investigate fermionic quantum criticality based on short-time dynamics, paving a promising avenue to fathoming quantum criticality in diverse fermionic systems with high efficiency.

Electronic Transport and Fermi Surface Topology of Zintl phase Dirac Semimetal SrZn2Ge2. (arXiv:2310.10621v1 [cond-mat.str-el])
M. K. Hooda (1), A. Chakraborty (1 and 2) S. Roy (3), A. Agarwal (1), P. Mandal (4), S. N. Sarangi (5), D. Samal (5 and 6), V. P. S. Awana (7), Z. Hossain (1) ((1) Department of Physics, Indian Institute of Technology, Kanpur-208016, India, (2) Institute of Physics, Johannes Gutenberg Universität, Staudinger Weg 7, 55128 Mainz, Germany, (3) Vidyasagar Metropolitan College, 39, Sankar Ghosh Lane, Kolkata 700006, India, (4) Department of Condensed Matter and Material Physics, S. N. Bose National Centre for Basic Sciences, Block JD, Sector III, Salt Lake, Kolkata 700106, India, (5) Institute of Physics, Bhubaneswar, Bhubaneswar-751005, India, (6) Homi Bhabha National Institute, Anushakti Nagar, Mumbai 400085, India, (7) CSIR National Physical Laboratory, New Delhi, 110012, India)

We report a comprehensive study on the electronic transport properties of SrZn$_2$Ge$_2$ single crystals. The in-plane electrical resistivity of the compound exhibits linear temperature dependence for 80 K < T < 300 K, and T^2 dependence below 40 K, consistent with the Fermi liquid behavior. Both the transverse and longitudinal magnetoresistance exhibit a crossover at critical field B* from weak-field quadratic-like to high-field unsaturated linear field dependence at low temperatures (T \leq 50 K). Different interpretations of this magnetoresistance crossover behavior are presented based on the quantum limit of Dirac Fermions and the specific topology of the Fermi surface of the compound. Abrikosov's theory is employed to explain linear behavior of magnetoresistance at low temperatures. The Hall resistivity data establish SrZn$_2$Ge$_2$ as a multiband system with contributions from both the electrons and holes. The Hall coefficient is observed to decrease with increasing temperature and magnetic field, changing its sign from positive to negative. The negative Hall coefficient observed at low temperatures in high fields and at high temperatures over the entire field range suggests that the highly mobile electron charge carriers dominate the electronic transport. Our first-principles calculations show that nontrivial topological surface states exist in SrZn$_2$Ge$_2$ within the bulk gap along the {\Gamma}-M path. Notably, these surface states extend from the valence to conduction band with their number varying based on the Sr and Ge termination plane. The Fermi surface of the compound exhibits a distinct tetragonal petal-like structure, with one open and several closed surfaces. Overall, these findings offer crucial insights into the mechanisms underlying the electronic transport of the compound.

Manipulating Metastability: Quenched Control of Topological Defects in Multiferroics. (arXiv:2310.10630v1 [cond-mat.mtrl-sci])
Nimish P. Nazirkar, Sowmya Srinivasan, Ross Harder, Edwin Fohtung

The topological properties of quasiparticles, such as skyrmions and vortices, have the potential to offer extraordinary metastability through topological protection, and drive motion with minimal electrical current excitation. This has promising implications for future applications in spintronics. Skyrmions frequently appear either in lattice form or as separate, isolated quasiparticles \cite{Tokura21}. Magnetic ferroelectrics, a subset of multiferroics that exhibit magnetically induced ferroelectricity, possess intriguing characteristics like magnetic (electric) field-controlled ferroelectric (magnetic) responses. Previous research based on Landau theory indicated the potential to stabilize metastable phases in multiferroic barium hexaferrite \cite{Karpov19}. We have successfully stabilized these meta-stable phases through magnetic quenching of hexaferrite nanoparticles, leading to the creation of compelling topological structures. The structural changes in individual BaFe$_{12}$O$_{19}$ nanocrystals were scrutinized using Bragg coherent diffractive imaging, granting us insight into the emergent topological structures in field-quenched multiferroics. Additionally, we explored why these structures are energetically preferable for the formation of metastable topological structures.

Role of magnetic ions in the thermal Hall effect of the paramagnetic insulator TmVO$_{4}$. (arXiv:2310.10643v1 [cond-mat.mtrl-sci])
Ashvini Vallipuram, Lu Chen, Emma Campillo, Manel Mezidi, Gaël Grissonnanche, Mark P. Zic, Yuntian Li, Ian R. Fisher, Jordan Baglo, Louis Taillefer

In a growing number of materials, phonons have been found to generate a thermal Hall effect, but the underlying mechanism remains unclear. Inspired by previous studies that revealed the importance of Tb$^{3+}$ ions in generating the thermal Hall effect of Tb$_{2}$Ti$_{2}$O$_{7}$, we investigated the role of Tm$^{3+}$ ions in TmVO$_{4}$, a paramagnetic insulator with a different crystal structure. We observe a negative thermal Hall conductivity in TmVO$_{4}$ with a magnitude such that the Hall angle, $|\kappa_{xy}$/$\kappa_{xx}|$, is approximately 1 x 10$^{-3}$ at $H$ = 15 T and $T$ = 20 K, typical for a phonon-generated thermal Hall effect. In contrast to the negligible $\kappa_{xy}$ found in Y$_{2}$Ti$_{2}$O$_{7}$, we observe a negative $\kappa_{xy}$ in YVO$_{4}$ with a Hall angle of magnitude comparable to that of TmVO$_{4}$. This shows that the Tm$^{3+}$ ions are not essential for the thermal Hall effect in this family of materials. Interestingly, at an intermediate Y concentration of 30 % in Tm$_{1-x}$Y$_{x}$VO$_{4}$, $\kappa_{xy}$ was found to have a positive sign, pointing to the possible importance of impurities in the thermal Hall effect of phonons.

Introduction to the "second quantization" formalism for non-relativistic quantum mechanics: A possible substitution for Sections 6.7 and 6.8 of Feynman's "Statistical Mechanics". (arXiv:1812.10732v5 [cond-mat.stat-mech] UPDATED)
Hal Tasaki

This is a self-contained and hopefully readable account on the method of creation and annihilation operators (also known as the Fock space representation or the "second quantization" formalism) for non-relativistic quantum mechanics of many particles. Assuming knowledge only on conventional quantum mechanics in the wave function formalism, we define the creation and annihilation operators, discuss their properties, and introduce corresponding representations of states and operators of many-particle systems. As the title of the note suggests, we cover most topics treated in sections 6.7 and 6.8 of Feynman's "Statistical Mechanics: A Set of Lectures". As a preliminary, we also carefully discuss the symmetry of wave functions describing indistinguishable particles.

We note that all the contents of the present note are completely standard, and the definitions and the derivations presented here have been known to many. Although the style of the present note may be slightly more mathematical than standard physics literatures, we do not try to achieve full mathematical rigor.(Note to experts: In particular we here DERIVE the (anti)commutation relations of the creation and annihilation operators, rather than simply declaring them. In this sense our approach is quite close to that of Feynman's. But we here focus on the action of creation/annihilation operators on general $N$ body wave functions, while Feynman makes a heavy use of Slater-determinant-type states from the beginning. We hope that our presentation provides a better perspective on the formalism.)

Electrical manipulation of valley-qubit and valley geometric phase in lateral monolayer heterostructures. (arXiv:2209.14445v2 [cond-mat.mes-hall] UPDATED)
Jarosław Pawłowski, John Eric Tiessen, Rockwell Dax, Junxia Shi

We explore a solid state qubit defined on valley isospin of electron confined in a gate-defined quantum dot created in an area of MoS$_2$/WS$_2$-monolayer lateral junction. We show that a properly oriented junction with respect to the monolayer lattice can induce intervalley transitions of electron confined in the neighboring quantum dot when overlapping with the junction is significant and pumping frequency tuned. The pumping scheme that induces transitions is all-electrical: obtained by applying oscillating voltages to control gates and thus enables for scalable qubit architectures. We also report another possibility of valley-qubit manipulation by accumulating non-Abelian Berry phase. To model nanodevice we solve the time-dependent Schr\"odinger equation in a tight-binding approach and obtain exact time-evolution of the valley-qubit system. During the evolution we simultaneously solve the Poisson equation in self-consistent manner with the Schr\"odinger equation, with the confinement potential controlled via voltages applied to the local gates.

Optically controlled single-valley exciton doublet states with tunable internal spin structures and spin magnetization generation. (arXiv:2211.03334v2 [cond-mat.mtrl-sci] UPDATED)
Jiawei Ruan, Zhenglu Li, Chin Shen Ong, Steven G. Louie

Manipulating quantum states through light-matter interactions has been actively pursued in two-dimensional (2D) materials research. Significant progress has been made towards the optical control of the valley degrees of freedom in semiconducting monolayer transition-metal dichalcogenides (TMD), based on doubly degenerate excitons from their two distinct valleys in reciprocal space. Here, we introduce a novel kind of optically controllable doubly degenerate exciton states that come from a single valley, dubbed as single-valley exciton doublet (SVXD) states. They are unique in that their constituent holes originate from the same valence band, making possible the direct optical control of the spin structure of the excited constituent electrons. Combining ab initio GW plus Bethe-Salpeter equation (GW-BSE) calculations and a newly developed theoretical analysis method, we demonstrate such novel SVXD in substrate-supported monolayer bismuthene -- which has been successfully grown using molecular beam epitaxy. In each of the two distinct valleys in the Brillouin zone, strong spin-orbit coupling and $C_{3v}$ symmetry lead to a pair of degenerate 1s exciton states (the SVXD states) with opposite spin configurations. Any coherent linear combinations of the SVXD in a single valley can be excited by light with a specific polarization, enabling full manipulation of their internal spin configurations. In particular, a controllable net spin magnetization can be generated through light excitation. Our findings open new routes to control quantum degrees of freedom, paving the way for applications in spintronics and quantum information science.

Tension Remodeling Controls Topological Transitions in Epithelial Tissues. (arXiv:2211.05591v2 [] UPDATED)
Fernanda Pérez-Verdugo, Shiladitya Banerjee

Cell neighbor exchanges play a critical role in regulating tissue fluidity during epithelial morphogenesis and repair. In vivo, these neighbor exchanges are often hindered by the formation of transiently stable four-fold vertices, which can develop into complex multicellular rosettes where five or more cell junctions meet. Despite their importance, the mechanical origins of multicellular rosettes have remained elusive, and current cellular models lack the ability to explain their formation and maintenance. Here we present a dynamic vertex model of epithelial tissues with strain-dependent tension remodeling and mechanical memory dissipation. We show that an increase in cell junction tension upon contraction and reduction in tension upon extension can stabilize higher-order vertices, temporarily stalling cell rearrangements. On the other hand, inducing mechanical memory dissipation via relaxation of junction strain and stress promotes the resolution of higher-order vertices, facilitating cell neighbor exchanges. We demonstrate that by tuning the rates of tension remodeling and mechanical memory dissipation, we can control topological transitions and tissue material properties, recapitulating complex cellular topologies seen in developing organisms.

Strain-induced Landau levels of Majorana fermions in an anisotropically interacting Kitaev model on a honeycomb lattice. (arXiv:2301.05330v2 [cond-mat.str-el] UPDATED)
Takuto Yamada, Sei-ichiro Suga

The energy structure of an anisotropically interacting Kitaev model on a honeycomb lattice under triaxial strain is investigated. A numerical calculation shows that quantized states appear in the low-energy region, even when the anisotropy of the interaction is rather strong. Their energies are proportional to the square root of the quantum number and the quantized state at zero energy appears only on one sublattice. These findings indicate the emergence of the strain-induced Landau levels of Majorana fermions, which is also confirmed by an analytical calculation. These Landau levels are stable, when the direction of triaxial strain is slightly changed from the bond direction.

Quantum estimation and remote charge sensing with a hole-spin qubit in silicon. (arXiv:2303.07161v3 [cond-mat.mes-hall] UPDATED)
Gaia Forghieri, Andrea Secchi, Andrea Bertoni, Paolo Bordone, Filippo Troiani

Hole-spin qubits in semiconductors represent a mature platform for quantum technological applications. Here we consider their use as quantum sensors, and specifically for inferring the presence and estimating the distance from the qubit of a remote charge. Different approaches are considered - based on the use of single or double quantum dots, ground and out-of-equilibrium states, Rabi and Ramsey measurements - and comparatively analyzed by means of the discrimination probability, and of the classical and quantum Fisher information. Detailed quantitative aspects result from the multiband character of the hole states, which we account for by means of the Luttinger-Kohn Hamiltonian. Furthermore, general conclusions can be drawn on the relative efficiency of the above options, and analytical expressions are derived for the Fisher information of a generic qubit within the Rabi and Ramsey schemes.

Charge order induced Dirac pockets in the nonsymmorphic crystal TaTe$_4$. (arXiv:2304.00425v3 [cond-mat.str-el] UPDATED)
Yichen Zhang, Ruixiang Zhou, Hanlin Wu, Ji Seop Oh, Sheng Li, Jianwei Huang, Jonathan D. Denlinger, Makoto Hashimoto, Donghui Lu, Sung-Kwan Mo, Kevin F. Kelly, Robert J. Birgeneau, Bing Lv, Gang Li, Ming Yi

The interplay between charge order (CO) and nontrivial band topology has spurred tremendous interest in understanding topological excitations beyond the single-particle description. In a quasi-one-dimensional nonsymmorphic crystal TaTe$_4$, the (2a$\times$2b$\times$3c) charge ordered ground state drives the system into a space group where the symmetry indicator features the emergence of Dirac fermions and unconventional double Dirac fermions. Using angle-resolved photoemission spectroscopy and first-principles calculations, we provide evidence of the CO induced Dirac fermion-related bands near the Fermi level. Furthermore, the band folding at the Fermi level is compatible with the new periodicity dictated by the CO, indicating that the electrons near the Fermi level follow the crystalline symmetries needed to host double Dirac fermions in this system.

Generalized Devil's staircase and RG flows. (arXiv:2304.07640v4 [cond-mat.stat-mech] UPDATED)
Ana Flack, Alexander Gorsky, Sergei Nechaev

We discuss a two-parameter renormalization group (RG) flow when parameters are organized in a single complex variable, $\tau$, with modular properties. Throughout the work we consider a special limit when the imaginary part of $\tau$ characterizing the disorder strength tends to zero. We argue that generalized Riemann-Thomae (gRT) function and the corresponding generalized Devil's staircase emerge naturally in a variety of physical models providing a universal behavior. In 1D we study the Anderson-like probe hopping in a weakly disordered lattice, recognize the origin of the gRT function in the spectral density of the probe and formulate specific RG procedure which gets mapped onto the discrete flow in the fundamental domain of the modular group $SL(2,Z)$. In 2D we consider the generalization of the phyllotaxis crystal model proposed by L. Levitov and suggest the explicit form of the effective potential for the probe particle propagating in the symmetric and asymmetric 2D lattice of defects. Analyzing the structure of RG flow equations in the vicinity of saddle points we claim emergence of BKT-like transitions at ${\rm Im}\,\tau\to 0$. We show that the RG-like dynamics in the fundamental domain of $SL(2,Z)$ for asymmetric lattices asymptotically approaches the "Silver ratio". For a Hubbard model of particles on a ring interacting via long-ranged potentials we investigate the dependence of the ground state energy on the potential and demonstrate by combining numerical and analytical tools the emergence of the generalized Devil's staircase. Also we conjecture a bridge between a Hubbard model and a phyllotaxis.

Antiferromagnetic Bloch line driven by spin current as room-temperature analog of a fluxon in a long Josephson junction. (arXiv:2305.02276v3 [cond-mat.mes-hall] UPDATED)
R.V. Ovcharov, B.A. Ivanov, J. Åkerman, R. S. Khymyn

Antiferromagnets (AFMs) are promising materials for future high-frequency field-free spintronic applications. Self-localized spin structures can enhance their capabilities and introduce new functionalities to AFM-based devices. Here we consider a domain wall (DW), a topological soliton that bridges a connection between two ground states, similar to a Josephson junction (JJ) link between two superconductors. We demonstrate the similarities between DWs in bi-axial AFM with easy-axis primary anisotropy, driven by a spin current, and long Josephson junctions (LJJs). We found that the Bloch line (BL) in DWs resembles the fluxon state of JJs, creating a close analogy between the two systems. We propose a scheme that allows us to create, move, read, and delete such BLs. This transmission line operates at room temperature and can be dynamically reconfigured in contrast to superconductors. Results of a developed model were confirmed by micromagnetic simulations for Cr$_2$O$_3$ and DyFeO$_3$, i.e., correspondingly with weak and strong in-plane anisotropy. Overall, the proposed scheme has significant potential for use in magnetic memory and logic devices.

Two-dimensional electron gases as non-Newtonian fluids. (arXiv:2305.02883v3 [cond-mat.str-el] UPDATED)
Serhii Kryhin, Leonid Levitov

Two-dimensional electron systems offer an appealing platform to explore long-lived excitations arising due to collinear carrier scattering enabled by phase-space constraints at the Fermi surface. Recently it was found that these effects can boost excitation lifetimes over the fundamental bound set by Landau's Fermi-liquid theory by a factor as large as $(T_F/T)^\alpha$ with $\alpha\approx 2$. Long-lived degrees of freedom possess the capability to amplify the response to weak perturbations, producing lasting collective memory effects. This leads to non-Newtonian hydrodynamics in 2D electron fluids driven by multiple viscous modes with scale-dependent viscosity. We describe these modes as Fermi surface modulations of odd parity evolving in space and time, and discuss their implications for experimental studies of electron hydrodynamics.

Generalized Charges, Part II: Non-Invertible Symmetries and the Symmetry TFT. (arXiv:2305.17159v2 [hep-th] UPDATED)
Lakshya Bhardwaj, Sakura Schafer-Nameki

Consider a d-dimensional quantum field theory (QFT) $\mathfrak{T}$, with a generalized symmetry $\mathcal{S}$, which may or may not be invertible. We study the action of $\mathcal{S}$ on generalized or $q$-charges, i.e. $q$-dimensional operators. The main result of this paper is that $q$-charges are characterized in terms of the topological defects of the Symmetry Topological Field Theory (SymTFT) of $\mathcal{S}$, also known as the ``Sandwich Construction''. The SymTFT is a $(d+1)$-dimensional topological field theory, which encodes the symmetry $\mathcal{S}$ and the physical theory in terms of its boundary conditions. Our proposal applies quite generally to any finite symmetry $\mathcal{S}$, including non-invertible, categorical symmetries. Mathematically, the topological defects of the SymTFT form the Drinfeld Center of the symmetry category $\mathcal{S}$. Applied to invertible symmetries, we recover the result of Part I of this series of papers. After providing general arguments for the identification of $q$-charges with the topological defects of the SymTFT, we develop this program in detail for QFTs in 2d (for general fusion category symmetries) and 3d (for fusion 2-category symmetries).

Bandgaps of insulators from moment-functional based spectral density-functional theory. (arXiv:2306.06259v3 [cond-mat.str-el] UPDATED)
Frank Freimuth, Stefan Blügel, Yuriy Mokrousov

Within the method of spectral moments it is possible to construct the spectral function of a many-electron system from the first $2P$ spectral moments ($P=1,2,3,\dots$). The case $P=1$ corresponds to standard Kohn-Sham density functional theory (KS-DFT). Taking $P>1$ allows us to consider additional important properties of the uniform electron gas (UEG) in the construction of suitable moment potentials for moment-functional based spectral density-functional theory (MFbSDFT). For example, the quasiparticle renormalization factor $Z$, which is not explicitly considered in KS-DFT, can be included easily. In the 4-pole approximation of the spectral function of the UEG (corresponding to $P=4$) we can reproduce the momentum distribution, the second spectral moment, and the charge response acceptably well, while a treatment of the UEG by KS-DFT reproduces from these properties only the charge response. For weakly and moderately correlated systems we may reproduce the most important aspects of the 4-pole approximation by an optimized two-pole model, which leaves away the low-energy satellite band. From the optimized two-pole model we extract \textit{parameter-free universal} moment potentials for MFbSDFT, which improve the description of the bandgaps in Si, SiC, BN, MgO, CaO, and ZnO significantly.

Multipolar spin liquid in an exactly solvable model for $j_\mathrm{eff} = \frac{3}{2}$ moments. (arXiv:2306.08624v2 [cond-mat.str-el] UPDATED)
Vanuildo S. de Carvalho, Hermann Freire, Rodrigo G. Pereira

We study an exactly solvable model with bond-directional quadrupolar and octupolar interactions between spin-orbital entangled $j_{\mathrm{eff}} = \frac{3}{2}$ moments on the honeycomb lattice. We show that this model features a multipolar spin liquid phase with gapless fermionic excitations. In the presence of perturbations that break time-reversal and rotation symmetries, we find Abelian and non-Abelian topological phases in which the Chern number evaluates to $0$, $\pm 1$, and $\pm 2$. We also investigate quantum phase transitions out of the multipolar spin liquid using a parton mean-field approach and orbital wave theory. In the regime of strong integrability-breaking interactions, the multipolar spin liquid gives way to ferroquadrupolar-vortex and antiferro-octupolar ordered phases that harbor a hidden spin-$\frac{1}{2}$ Kitaev spin liquid. Our work unveils mechanisms for unusual multipolar orders and quantum spin liquids in Mott insulators with strong spin-orbit coupling.

Monopole-like orbital-momentum locking and the induced orbital transport in topological chiral semimetals. (arXiv:2307.02668v2 [cond-mat.mes-hall] UPDATED)
Qun Yang, Jiewen Xiao, Iñigo Robredo, Maia G. Vergniory, Binghai Yan, Claudia Felser

The interplay between chirality and topology nurtures many exotic electronic properties. For instance, topological chiral semimetals display multifold chiral fermions that manifest nontrivial topological charge and spin texture. They are an ideal playground for exploring chirality-driven exotic physical phenomena. In this work, we reveal a monopole-like orbital-momentum locking texture on the three-dimensional Fermi surfaces of topological chiral semimetals with B20 structures (e.g., RhSi and PdGa). This orbital texture enables a large orbital Hall effect (OHE) and a giant orbital magnetoelectric (OME) effect in the presence of current flow. Different enantiomers exhibit the same OHE which can be converted to the spin Hall effect by spin-orbit coupling in materials. In contrast, the OME effect is chirality-dependent and much larger than its spin counterpart. Our work reveals the crucial role of orbital texture for understanding OHE and OME effects in topological chiral semimetals and paves the path for applications in orbitronics, spintronics, and enantiomer recognition.

Pseudo-magnetic fields in square lattices. (arXiv:2309.00212v2 [cond-mat.mes-hall] UPDATED)
Junsong Sun, Xingchuan Zhu, Tianyu Liu, Shiping Feng, Huaiming Guo

We have investigated the effects of strain on two-dimensional square lattices and examined the methods for inducing pseudo-magnetic fields. In both the columnar and staggered $\pi$-flux square lattices, we have found that strain only modulates Fermi velocities rather than inducing pseudo-magnetic fields. However, spatially non-uniform on-site potentials (anisotropic hoppings) can create pseudo-magnetic fields in columnar (staggered) $\pi$-flux square lattices. On the other hand, we demonstrate that strain does induce pseudo-magnetic fields in staggered zero-flux square lattices. By breaking a quarter of the bonds, we clarify that a staggered zero-flux square lattice is topologically equivalent to a honeycomb lattice and displays pseudo-vector potentials and pseudo-Landau levels at the Dirac points.

Quantum Materials Group Annual Report 2022. (arXiv:2310.00456v2 [cond-mat.mes-hall] UPDATED)
P. Kumari, S. Rani, S. Kar, T. Mukherjee, S. Majumder, K. Kumari, S. J. Ray

The Quantum Materials group at Indian Institute of Technology Patna is working on a range of topics relating to nanoelectronics, spintronics, clean energy and memory design etc. The PI has past experiences of working extensively with superconducting systems like cuprates [1, 2], ruthanate [3], pnictide [4, 5], thin film heterostructures [6, 7] etc and magnetic recording media [8, 9] etc. In this report, we have summarised the ongoing works in our group. We explored a range of functional materials like two-dimensional materials, oxides. topological insulators, organic materials etc. using a combination of experimnetal and computational tools. Some of the useful highlights are as follows: (a) tuning and control of the magnetic and electronic state of 2D magentic materials with rapid enhancement in the Curie temperature, (b) Design and detection of single electron transistor based nanosensors for the detection of biological species with single molecular resolution, (c) Observation of non-volatile memory behaviour in the hybrid structures made of perovskite materials and 2D hybrids. The results offer useful insight in the design of nanoelectronic architecrures for diverse applications.

Found 8 papers in prb
Date of feed: Tue, 17 Oct 2023 03:17:02 GMT

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

Evidence for a conical spin spiral state in the Mn triple layer on W(001): Spin-polarized scanning tunneling microscopy and first-principles calculations
Paula M. Weber, Tim Drevelow, Jing Qi, Matthias Bode, and Stefan Heinze
Author(s): Paula M. Weber, Tim Drevelow, Jing Qi, Matthias Bode, and Stefan Heinze

The spin structure of a Mn triple layer grown pseudomorphically on a W(001) surface is studied using spin-polarized scanning tunneling microscopy (SP-STM) and density functional theory (DFT). In SP-STM images a $\mathrm{c}(4×2)$ superstructure is found. The magnetic origin of this contrast is verifi…

[Phys. Rev. B 108, 134419] Published Mon Oct 16, 2023

Crystal structure and magnetic properties of the spin-$\frac{1}{2}$ frustrated two-leg ladder compounds $({\mathrm{C}}_{4}{\mathrm{H}}_{14}{\mathrm{N}}_{2}){\mathrm{Cu}}_{2}{X}_{6}$ $(X=\mathrm{Cl} \text{and} \mathrm{Br})$
P. Biswal, S. Guchhait, S. Ghosh, S. N. Sarangi, D. Samal, Diptikanta Swain, Manoranjan Kumar, and R. Nath
Author(s): P. Biswal, S. Guchhait, S. Ghosh, S. N. Sarangi, D. Samal, Diptikanta Swain, Manoranjan Kumar, and R. Nath

We have successfully synthesized single crystals, solved the crystal structure, and studied the magnetic properties of a new family of copper halides $({\mathrm{C}}_{4}{\mathrm{H}}_{14}{\mathrm{N}}_{2}){\mathrm{Cu}}_{2}{X}_{6}$ $(X=\mathrm{Cl},\mathrm{Br})$. These compounds crystallize in an orthorh…

[Phys. Rev. B 108, 134420] Published Mon Oct 16, 2023

Benchmarking density functional theory on the prediction of antiferromagnetic transition temperatures
Zahra Mosleh and Mojtaba Alaei
Author(s): Zahra Mosleh and Mojtaba Alaei

This study investigates the predictive capabilities of common density functional theory (DFT) methods (GGA, $\mathrm{GGA}+U$, and $\mathrm{GGA}+U+V$) for determining the transition temperature of antiferromagnetic insulators. We utilize a data set of 29 compounds and derive Heisenberg exchanges base…

[Phys. Rev. B 108, 144413] Published Mon Oct 16, 2023

Quantum Fisher information and multipartite entanglement in spin-1 chains
Federico Dell'Anna, Sunny Pradhan, Cristian Degli Esposti Boschi, and Elisa Ercolessi
Author(s): Federico Dell'Anna, Sunny Pradhan, Cristian Degli Esposti Boschi, and Elisa Ercolessi

In this paper, we study the ground-state quantum Fisher information (QFI) in one-dimensional spin-1 models, as witness to multipartite entanglement. The models addressed are the bilinear-biquadratic model, the most general isotropic $\text{SU}(2)$-invariant spin-1 chain, and the $XXZ$ spin-1 chain, …

[Phys. Rev. B 108, 144414] Published Mon Oct 16, 2023

Edge-enhanced negative magnetoresistance in a $\mathrm{W}{\mathrm{Se}}_{2}/\mathrm{F}{\mathrm{e}}_{3}\mathrm{Ge}{\mathrm{Te}}_{2}$ heterostructure
Xin Liao, Zhen-Cun Pan, Chun-Guang Chu, Tong-Yang Zhao, An-Qi Wang, and Zhi-Min Liao
Author(s): Xin Liao, Zhen-Cun Pan, Chun-Guang Chu, Tong-Yang Zhao, An-Qi Wang, and Zhi-Min Liao

Dzyaloshinskii-Moriya interaction (DMI), the antisymmetric exchange interaction in noncentrosymmetric magnets, is a key ingredient in forming and manipulating the magnetic skyrmion, a promising candidate for next-generation data storage. With the development of non-Hermitian topological phases, the …

[Phys. Rev. B 108, 144416] Published Mon Oct 16, 2023

Fractonic higher-order topological phases in open quantum systems
Jian-Hao Zhang, Ke Ding, Shuo Yang, and Zhen Bi
Author(s): Jian-Hao Zhang, Ke Ding, Shuo Yang, and Zhen Bi

In this work, we study the generalization of decohered average symmetry-protected topological phases to open quantum systems with a combination of subsystem symmetries and global symmetries. In particular, we provide examples of two types of intrinsic average higher-order topological phases with ave…

[Phys. Rev. B 108, 155123] Published Mon Oct 16, 2023

Magnetic field driven Lifshitz transition and one-dimensional Weyl nodes in three-dimensional pentatellurides
Zhigang Cai and Yi-Xiang Wang
Author(s): Zhigang Cai and Yi-Xiang Wang

Recent experiments reported that the magnetic field can drive the Lifshitz transition and one-dimensional (1D) Weyl nodes in the quantum limit of three-dimensional pentatellurides, as they own low carrier densities and can achieve the extreme quantum limit at a low magnetic field. In this paper, we …

[Phys. Rev. B 108, 155202] Published Mon Oct 16, 2023

Acoustic corner state transfer mapping to synthetic higher-order topological semimetal
Hui Liu, Haonan Wang, Boyang Xie, Hua Cheng, Zhengyou Liu, and Shuqi Chen
Author(s): Hui Liu, Haonan Wang, Boyang Xie, Hua Cheng, Zhengyou Liu, and Shuqi Chen

The robust transport of quantized particles in gap systems through adiabatic cyclic evolution corresponds to dynamical versions of topological insulators, which have recently emerged as a thriving topic. Until now, these connections were thought to be limited to gap systems. Here, we report a mechan…

[Phys. Rev. B 108, L161104] Published Mon Oct 16, 2023

Found 1 papers in prl
Date of feed: Tue, 17 Oct 2023 03:17:00 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)

Nonlinear Topological Magnon Spin Hall Effect
Zhejunyu Jin, Xianglong Yao, Zhenyu Wang, H. Y. Yuan, Zhaozhuo Zeng, Weiwei Wang, Yunshan Cao, and Peng Yan
Author(s): Zhejunyu Jin, Xianglong Yao, Zhenyu Wang, H. Y. Yuan, Zhaozhuo Zeng, Weiwei Wang, Yunshan Cao, and Peng Yan

Nonlinear scattering of magnons and skyrmions in antiferromagnets leads to a spin Hall effect that emerges from real-space topology.

[Phys. Rev. Lett. 131, 166704] Published Mon Oct 16, 2023

Found 2 papers in pr_res
Date of feed: Tue, 17 Oct 2023 03:17:02 GMT

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

Fractional transconductance via nonadiabatic topological Cooper pair pumping
Hannes Weisbrich, Raffael L. Klees, Oded Zilberberg, and Wolfgang Belzig
Author(s): Hannes Weisbrich, Raffael L. Klees, Oded Zilberberg, and Wolfgang Belzig

Many robust physical phenomena in quantum physics are based on topological invariants arising due to intriguing geometrical properties of quantum states. Prime examples are the integer and fractional quantum Hall effects that demonstrate quantized Hall conductances, associated with topology both in …

[Phys. Rev. Research 5, 043045] Published Mon Oct 16, 2023

Experimental characterization of a single-shot spectrometer for high-flux, GeV-scale gamma-ray beams
N. Cavanagh, K. Fleck, M. J. V. Streeter, E. Gerstmayr, L. T. Dickson, C. Ballage, R. Cadas, L. Calvin, S. Dobosz Dufrénoy, I. Moulanier, L. Romagnani, O. Vasilovici, A. Whitehead, A. Specka, B. Cros, and G. Sarri
Author(s): N. Cavanagh, K. Fleck, M. J. V. Streeter, E. Gerstmayr, L. T. Dickson, C. Ballage, R. Cadas, L. Calvin, S. Dobosz Dufrénoy, I. Moulanier, L. Romagnani, O. Vasilovici, A. Whitehead, A. Specka, B. Cros, and G. Sarri

We report on the first experimental characterization of a gamma-ray spectrometer designed to spectrally resolve high-flux photon beams with energies in the GeV range. The spectrometer has been experimentally characterized using a bremsstrahlung source obtained at the Apollon laser facility during th…

[Phys. Rev. Research 5, 043046] Published Mon Oct 16, 2023

Found 3 papers in comm-phys

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

Ab-initio simulations of coherent phonon-induced pumping of carriers in zirconium pentatelluride
Yong-Xin Yao

Communications Physics, Published online: 14 October 2023; doi:10.1038/s42005-023-01415-6

Coherent phonons can modify the wavefunction topology of quantum materials, yet the implications for electron dynamics remain to be addressed. The authors use time-dependent approaches to simulate the effect of coherent phonons, induced by strong terahertz laser field, on the electronic carrier dynamics in the topological insulator Zirconium Pentatelluride.

Investigating the Cuprates as a platform for high-order Van Hove singularities and flat-band physics
Arun Bansil

Communications Physics, Published online: 13 October 2023; doi:10.1038/s42005-023-01373-z

High-order Van Hove singularities (hoVHSs) with power-law divergences in the density-of-states are drawing current interest mainly in context of two-dimensional (2D) twisted moiré materials. Using cuprate high-Tc superconductors as an example, here the authors illustrate complications that can arise in bulk materials in defining hoVHSs and the need to extend the definition of hoVHSs to include flat-band materials.

Spontaneous superconducting diode effect in non-magnetic Nb/Ru/Sr2RuO4 topological junctions
Yoshiteru Maeno

Communications Physics, Published online: 13 October 2023; doi:10.1038/s42005-023-01409-4

Non-reciprocal electronic transport in a superconducting device is known as superconducting diode effect, which has potential for dissipationless electronics and computing. Previously, conventional superconductors have been used. Here, authors present their findings of such an effect in devices based on an unconventional superconductor Sr2RuO4 that may break time reversal symmetry.