Found 39 papers in cond-mat
Date of feed: Fri, 22 Dec 2023 01:30:00 GMT

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Bosonization and Anomaly Indicators of (2+1)-D Fermionic Topological Orders. (arXiv:2312.13341v1 [math-ph])
Arun Debray, Weicheng Ye, Matthew Yu

We provide a mathematical proposal for the anomaly indicators of symmetries of (2+1)-d fermionic topological orders, and work out the consequences of our proposal in several nontrivial examples. Our proposal is an invariant of a super modular tensor category with a fermionic group action, which gives a (3+1)-d topological field theory (TFT) that we conjecture to be invertible; the anomaly indicators are partition functions of this TFT on $4$-manifolds generating the corresponding twisted spin bordism group. Our construction relies on a bosonization construction due to Gaiotto-Kapustin and Tata-Kobayashi-Bulmash-Barkeshli, together with a ``bosonization conjecture'' which we explain in detail. In the second half of the paper, we discuss several examples of our invariants relevant to condensed-matter physics. The most important example we consider is $\mathbb{Z}/4^T\times \mathbb{Z}/2^f$ time-reversal symmetry with symmetry algebra $\mathcal T^2 = (-1)^FC$, which many fermionic topological orders enjoy, including the $\mathrm{U}(1)_5$ spin Chern-Simons theory. Using newly developed tools involving the Smith long exact sequence, we calculate the cobordism group that classifies its anomaly, present the generating manifold, and calculate the partition function on the generating manifold which serves as our anomaly indicator. Our approach allows us to reproduce anomaly indicators known in the literature with simpler proofs, including $\mathbb{Z}/4^{Tf}$ time-reversal symmetry with symmetry algebra $\mathcal T^2 = (-1)^F$, and other symmetry groups in the 10-fold way involving Lie group symmetries.

Entanglement smectic and stripe order. (arXiv:2312.13362v1 [cond-mat.mes-hall])
Nilotpal Chakraborty, Roderich Moessner, Benoit Doucot

Spontaneous symmetry breaking and more recently entanglement are two cornerstones of quantum matter. We introduce the notion of anisotropic entanglement ordered phases, where the spatial profile of spin-pseudospin entanglement spontaneously lowers the four-fold rotational symmetry of the underlying crystal to a two-fold one, while the charge density retains the full symmetry. The resulting phases, which we term $\textit{entanglement smectic}$ and $\textit{entanglement stripe}$, exhibit a rich Goldstone mode spectrum and a set of phase transitions as a function of underlying anisotropies. We discuss experimental consequences of such anisotropic entanglement phases distinguishing them from more conventional charge or spin stripes. Our discussion of this interplay between entanglement and spontaneous symmetry breaking focuses on multicomponent quantum Hall systems realizing textured Wigner crystals, as may occur in graphene or possibly also in moir\'e systems, highlighting the rich landscape and properties of possible entanglement ordered phases.

Topological Superconductivity in Twisted Flakes of Nodal Superconductors. (arXiv:2312.13367v1 [cond-mat.supr-con])
Kevin P. Lucht, J. H. Pixley, Pavel A. Volkov

Twisted bilayers of nodal superconductors have been recently demonstrated to be a potential platform to realize two-dimensional topological superconductivity. Here we study the topological properties of twisted finite-thickness flakes of nodal superconductors under applied current, focusing on the case of a $N$-layer flake with a single twisted top layer. At low current bias and small twist angles, the average nodal topological gap is reduced with flake thickness as $\sim\mathcal{O}(\frac{1}{N})$, but the Chern number grows $\sim \mathcal{O}(N)$. As a result, we find the thermal Hall coefficient to be independent of $N$ at temperatures larger than the nodal gap. At larger twist angles, we demonstrate that the nodal gap in the density of states of the top layer is only weakly suppressed, allowing its detection in scanning tunneling microscopy experiments. These conclusions are demonstrated numerically in an atomic-scale tight-binding model and analytically through the model's continuum limit, finding excellent agreement between the two. Finally, we show that increasing the bias current leads to a sequence of topological transitions, where the Chern number increases like $\sim\mathcal{O}(N^2)$ beyond the additive effect of stacking $N$ layers. Our results show that twisted superconductor flakes are "$2.5$-dimensional" materials, allowing to realize new electronic properties due to synergy between two-dimensional layers extended to a finite thickness in a third dimension.

Quantum Scars and Caustics in Majorana Billiards. (arXiv:2312.13368v1 [cond-mat.mes-hall])
R. Johanna Zijderveld, A. Mert Bozkurt, Michael Wimmer, İnanç Adagideli

We demonstrate that the classical dynamics influence the localization behaviour of Majorana wavefunctions in Majorana billiards. By using a connection between Majorana wavefunctions and eigenfunctions of a normal state Hamiltonian, we show that Majorana wavefunctions in both p-wave and s-wave topological superconductors inherit the properties of the underlying normal state eigenfunctions. As an example, we demonstrate that Majorana wavefunctions in topological superconductors with chaotic shapes feature quantum scarring. Furthermore, we show a way to manipulate a localized Majorana wavefunction by altering the underlying classical dynamics using a local potential away from the localization region. Finally, in the presence of chiral symmetry breaking, we find that the Majorana wavefunction in convex-shaped Majorana billiards exhibits caustics formation, reminiscent of a normal state system with magnetic field.

Integrable-to-Thermalizing Crossover in Non-Equilibrium Superconductors. (arXiv:2312.13391v1 [cond-mat.supr-con])
Andrey Grankin, Victor Galitski

Motivated by the experiment by M. Budden {\em et al.} [Nature Physics {\bf 17}, 611 (2021)], who observed signatures of long-lived photo-induced superconductivity, we develop an accurate analytical/computational approach to non-equilibrium superconductivity following a quench. We consider the BCS-Holstein model, which includes both integrable local electron-electron interactions and integrability-breaking electron-phonon coupling. We develop Keldysh-Eliashberg theory on the Kadanoff-Baym contour, which enables us to describe non-equilibrium dynamics of the superconductor. We consider a quench in interactions, which results in a dynamic transition from the initial superconducting state to a normal thermal state in the end of the evolution. It is shown that the dynamics contain two stages: The early-time integrable behavior, involving coherent oscillations of the superconducting order parameter, crosses over to the late-time ergodic dynamics exhibiting a thermal decay into an equilibrium state. In the former regime, our computational approach both reproduces exact analytical results on the integrable dynamics of the order parameter and generalizes those to the case of an initial thermal state. The method also succeeds for the first time in describing both integrable-to-thermalizing crossover and the late-time thermal decay, which is shown to be consistent with the time-dependent Ginzburg-Landau theory (with the exponential decay time dependent on the density of quasiparticle excitations). We observe the electron distribution function approaching the Fermi-Dirac thermal distribution at final stages. The details of two-time non-equilibrium dynamics depend on the density of quasiparticles in the initial state and the integrability-breaking parameters, which under certain conditions may result in a long-lived transient superconductivity consistent with experiment.

Ultraclean two-dimensional hole systems with mobilities exceeding 10$^7$ cm$^2$/Vs. (arXiv:2312.13491v1 [cond-mat.mes-hall])
Adbhut Gupta, C. Wang, S.K. Singh, K.W. Baldwin, R. Winkler, M. Shayegan, L.N. Pfeiffer

Owing to their large effective mass, strong and tunable spin-orbit coupling, and complex band-structure, two-dimensional hole systems (2DHSs) in GaAs quantum wells provide rich platforms to probe exotic many-body physics, while also offering potential applications in ballistic and spintronics devices, and fault-tolerant topological quantum computing. We present here a systematic study of molecular-beam-epitaxy grown, modulation-doped, GaAs (001) 2DHSs where we explore the limits of low-temperature 2DHS mobility by optimizing two parameters, the GaAs quantum well width and the alloy fraction ($x$) of the flanking Al$_x$Ga$_{1-x}$As barriers. We obtain a breakthrough in 2DHS mobility, with a peak value $\simeq 18 \times 10^6$ cm$^2$/Vs at a density of 3.8 $\times$ 10$^{10}$ /cm$^{2}$, implying a mean-free-path of $\simeq 57 \mu$m. Using transport calculations tailored to our structures, we analyze the operating scattering mechanisms to explain the non-monotonic evolution of mobility with density. We find it imperative to include the dependence of effective mass on 2DHS density, well width, and $x$. We observe concomitant improvement in quality as evinced by the appearance of delicate fractional quantum Hall states at very low density.

Revisit the phase diagram and piezoelectricity of lead zirconate titanate from first principles. (arXiv:2312.13518v1 [cond-mat.mtrl-sci])
Yubai Shi, Ri He, Bingwen Zhang, Zhicheng Zhong

Lead zirconate titanate (PbZr1-xTixO3, PZT) exhibits excellent piezoelectric properties in the morphotropic phase boundary (MPB) region of its temperature-composition phase diagram. However, the microscopic origin of its high piezoelectric response remains controversial. Here, we develop a machine-learning-based deep potential (DP) model of PZT using the training dataset from first principles density functional theory calculations. Based on DP-assisted large-scale atomic simulations, we reproduce the temperature-composition phase diagram of PZT, in good agreement with the experiment except the absence of structural transition from R3c to R3m. We find that the rhombohedral phase maintains R3c symmetry with slight oxygen octahedral tilting as increase of temperature, instead of appearing R3m symmetry. This discrepancy can trace back to the lack of experimental measurements to identify such slight octahedral tilting. More importantly, we clarify the atomic-level feature of PZT at the MPB, exhibiting the competing coupling of ferroelectric nanodomains with various polarization orientations. The high piezoelectric response is driven by polarization rotation of nanodomains induced by an external electric field.

Quantum electrodynamics under a quench. (arXiv:2312.13531v1 [cond-mat.stat-mech])
Ming-Rui Li, Shao-Kai Jian

Quantum electrodynamics (QED) is a cornerstone of particle physics and also finds diverse applications in condensed matter systems. Despite its significance, the dynamics of quantum electrodynamics under a quantum quench remains inadequately explored. In this paper, we investigate the nonequilibrium regime of quantum electrodynamics following a global quantum quench. Specifically, a massive Dirac fermion is quenched to a gapless state with an interaction with gauge bosons. In stark contrast to equilibrium (3+1)-dimensional QED with gapless Dirac fermions, where the coupling is marginally irrelevant, we identify a nonequilibrium fixed point characterized by nonFermi liquid behavior. Notably, the anomalous dimension at this fixed point varies with the initial quench parameter, suggesting an interesting quantum memory effect in a strongly interacting system. Additionally, we propose distinctive experimental signatures for nonequilibrium quantum electrodynamics.

Contribution of Graphene Molecules C$_{53}$ C$_{52}$ C$_{51}$ on Astronomical Diffuse Interstellar Bands (DIB). (arXiv:2312.13550v1 [astro-ph.GA])
Norio Ota

This molecular orbital analysis predicts that pure carbon graphene molecules would play an important role on astronomically observed Diffuse Interstellar Bands (DIB), rather than fullerene. Laboratory experiments precisely coincided with observed DIB bands as studied by E. Cambell et al., which were considered to originate from mono-cation fullerene-(C$_{60}$)$^{1+}$. To check theoretically a molecular orbital excitation of (C$_{60}$)$^{1+}$ was calculated by the Time-Dependent DFT. Calculated two bands were close to observed DIBs, but there were two problems, that the oscillator strength was zero, and that other three DIBs could not be reproduced. Laboratory experiments was the mass spectroscopic one filtering m/e=724, to suggest fullerene-(C$_{60}$)$^{1+}$ combined with He. However, there were other capabilities, as like He-atom intercalated 3D-graphite, [graphene(C$_{53}$)$^{1+}$--He--(C$_7$)], [graphene(C$_{51}$)$^{1+}$--He--(C$_9$)] and so on. A family of graphene (C$_{53}$), (C$_{52}$) and (C$_{51}$) was calculated. Results show that an astronomically observed 957.74nm band was reproduced well by calculated 957.74nm, also confirmed by laboratory experiment of 957.75nm. Other observed 963.26, 936.57 and 934.85nm bands were calculated to be 963.08, 935.89 and 933.72nm. Moreover, experimental 922.27nm band was calculated to be 922.02nm, which is not yet astronomically observed. Similarly, experimental 925.96, 912.80, 909.71 and 908.40nm bands were calculated to 926.01, 912.52, 910.32 and 908.55nm. It should be emphasized that graphene molecules may be ubiquitously floating in interstellar space.

The anomalous Floquet Anderson insulator in a continuously driven optical lattice. (arXiv:2312.13589v1 [cond-mat.quant-gas])
Arijit Dutta, Efe Sen, Jun-Hui Zheng, Monika Aidelsburger, Walter Hofstetter

The anomalous Floquet Anderson insulator (AFAI) has been theoretically predicted in step-wise periodically driven models, but its stability under more general driving protocols hasn't been determined. We show that adding disorder to the anomalous Floquet topological insulator realized with a continuous driving protocol in the experiment by K. Wintersperger et. al., Nat. Phys. $\textbf{16}$, 1058 (2020), supports an AFAI phase, where, for a range of disorder strengths, all the time averaged bulk states become localized, while the pumped charge in a Laughlin pump setup remains quantized.

Entanglement of edge modes in (very) strongly correlated topological insulators. (arXiv:2312.13598v1 [cond-mat.str-el])
Nisa Ara, Emil Mathew, Rudranil Basu, Indrakshi Raychowdhury

Identifying topological phases for a strongly correlated theory remains a non-trivial task, as defining order parameters, such as Berry phases, is not straightforward. Quantum information theory is capable of identifying topological phases for a theory that exhibits quantum phase transition with a suitable definition of order parameters that are related to different entanglement measures for the system. In this work, we study entanglement entropy for a bi-layer SSH model, both in the presence and absence of Hubbard interaction and at varying interaction strengths. For the free theory, edge entanglement acts as an order parameter, which is supported by analytic calculations and numerical (DMRG) studies. We calculate the symmetry-resolved entanglement and demonstrate the equipartition of entanglement for this model which itself acts as an order parameter when calculated for the edge modes. As the DMRG calculation allows one to go beyond the free theory, we study the entanglement structure of the edge modes in the presence of on-site Hubbard interaction for the same model. A sudden reduction of edge entanglement is obtained as interaction is switched on. The explanation for this lies in the change in the size of the degenerate subspaces in the presence and absence of interaction. We also study the signature of entanglement when the interaction strength becomes extremely strong and demonstrate that the edge entanglement remains protected. In this limit, the energy eigenstates essentially become a tensor product state, implying zero entanglement. However, a remnant entropy survives in the non-trivial topological phase which is exactly due to the entanglement of the edge modes.

Layer-dependent evolution of electronic structures and correlations in rhombohedral multilayer graphene. (arXiv:2312.13637v1 [cond-mat.mes-hall])
Yue-Ying Zhou, Yang Zhang, Shihao Zhang, Hao Cai, Ling-Hui Tong, Yuan Tian, Tongtong Chen, Qiwei Tian, Chen Zhang, Yiliu Wang, Xuming Zou, Xingqiang Liu, Yuanyuan Hu, Li Zhang, Lijie Zhang, Wen-Xiao Wang, Lei Liao, Zhihui Qin, Long-Jing Yin

The recent discovery of superconductivity and magnetism in trilayer rhombohedral graphene (RG) establishes an ideal, untwisted platform to study strong correlation electronic phenomena. However, the correlated effects in multilayer RG have received limited attention, and, particularly, the evolution of the correlations with increasing layer number remains an unresolved question. Here, we show the observation of layer-dependent electronic structures and correlations in RG multilayers from 3 to 9 layers by using scanning tunneling microscopy and spectroscopy. We explicitly determine layer-enhanced low-energy flat bands and interlayer coupling strength. The former directly demonstrates the further flattening of low-energy bands in thicker RG, and the later indicates the presence of varying interlayer interactions in RG multilayers. Moreover, we find significant splitting of the flat bands, ranging from ~50-80 meV, under liquid nitrogen temperature when they are partially filled, indicating the emergence of interaction-induced strongly correlated states. Particularly, the strength of the correlated states is notably enhanced in thicker RG and reaches its maximum in the six-layer, validating directly theoretical predictions and establishing abundant new candidates for strongly correlated systems. Our results provide valuable insights into the layer dependence of the electronic properties in RG, paving the way for investigating robust and highly accessible correlated phases in simpler systems.

Pattern formation in charge density wave states after a quantum quench. (arXiv:2312.13727v1 [cond-mat.stat-mech])
Lingyu Yang, Yang Yang, Gia-Wei Chern

We study post-quench dynamics of charge-density-wave (CDW) order in the square-lattice $t$-$V$ model. The ground state of this system at half-filling is characterized by a checkerboard modulation of particle density. A generalized self-consistent mean-field method, based on the time-dependent variational principle, is employed to describe the dynamical evolution of the CDW states. Assuming a homogeneous CDW order throughout the quench process, the time-dependent mean-field approach is reduced to the Anderson pseudospin method. Quench simulations based on the Bloch equation for pseudospins produce three canonical behaviors of order-parameter dynamics: phase-locked persistent oscillation, Landau-damped oscillation, and dynamical vanishing of the CDW order. We further develop an efficient real-space von Neumann equation method to incorporate dynamical inhomogeneity into simulations of quantum quenches. Our large-scale simulations uncover complex pattern formations in the post-quench CDW states, especially in the strong quench regime. The emergent spatial textures are characterized by super density modulations on top of the short-period checkerboard CDW order. Our demonstration of pattern formation in quenched CDW states, described by a simple broken $Z_2$ symmetry, underscores the importance of dynamical inhomogeneity in quantum quenches of many-body systems with more complex orders.

Hierarchical Topological States in Thermal Diffusive Networks. (arXiv:2312.13733v1 [cond-mat.supr-con])
Bao Chen, Kaiyun Pang, Ru Zheng, Feng Liu

The integration of topological concepts into electronic energy band theory has been a transformative development in condensed matter physics. Since then, this paradigm has broadened its reach, extending to a variety of physical systems, including open ones. In this study, we employ analogues of the generalized $n$-dimensional Su-Schrieffer-Heeger model, a cornerstone in understanding topological insulators and higher-order topological states, to unveil a dimensional hierarchy of topological states within thermal diffusive networks. Unlike their electronic counterparts, the topological states in these networks are characterized by confined temperature profiles of dimension $(n-d)$ with constant diffusive rates, where $n$ represents the system's dimension and $d$ is the order of the topological state. Our findings demonstrate the existence of topological corner states in thermal diffusive systems up to $n=3$, along with surface and hinge states. We also identify and discuss an intermediate-order topological phase in the case $n=3$, characterized by the presence of hinge states but the absence of corner states. Furthermore, our work delves into the influence of chiral symmetry in these thermal networks, particularly focusing on topological thermal states with a near-zero diffusion rate. This research lays the foundation for advanced thermal management strategies that utilize topological states in multiple dimensions.

Quantum confinement in Dirac-like nanostructures. (arXiv:2312.13748v1 [cond-mat.mes-hall])
C. A. Downing, M. E. Portnoi

In Westminster Abbey, in a nave near to Newton's monument, lies a memorial stone to Paul Dirac. The inscription on the stone includes the relativistic wave equation for an electron: the Dirac equation. At the turn of the 21st century, it was discovered that this eponymous equation was not simply the preserve of particle physics. The isolation of graphene by Andre Geim and Konstantin Novoselov in Manchester led to the exploration of a novel class of materials - Dirac materials - whose electrons behave like Dirac particles. While the mobility of these quasi-relativistic electrons is attractive from the perspective of potential ultrafast devices, it also presents a distinct challenge: how to confine Dirac particles so as to avoid making inherently leaky devices? Here we discuss the unconventional quantum tunnelling of Dirac particles, we explain a strategy to create bound states electrostatically, and we briefly review some pioneering experiments seeking to trap Dirac electrons.

Anomalies and Persistent Order in the Chiral Gross-Neveu model. (arXiv:2312.13756v1 [hep-th])
Riccardo Ciccone, Lorenzo Di Pietro, Marco Serone

We study the $2d$ chiral Gross-Neveu model at finite temperature $T$ and chemical potential $\mu$. The analysis is performed by relating the theory to a $SU(N)\times U(1)$ Wess-Zumino-Witten model with appropriate levels and global identifications necessary to keep track of the fermion spin structures. We study the two-point function of a certain composite fermion operator which allows us to determine the remnants for $T>0$ of the inhomogeneous chiral phase configuration found for any $N$ at $T=0$. The inhomogeneous configuration decays exponentially at large distances for anti-periodic fermions while, as a consequence of a certain $\mathbb{Z}_2$-valued 't Hooft anomaly, it persists for any $T>0$ and $\mu$ for periodic fermions. A large $N$ analysis confirms the above findings.

Enhanced elastic stability of a topologically disordered crystalline metal--organic framework. (arXiv:2312.13846v1 [cond-mat.mtrl-sci])
Emily G. Meekel, Phillippa Partridge, Robert A. I. Paraoan, Joshua J. B. Levinsky, Ben Slater, Claire L. Hobday, Andrew L. Goodwin

By virtue of their open network structures and low densities, metal--organic frameworks (MOFs) are soft materials that exhibit elastic instabilities at low applied stresses. The conventional strategy for improving elastic stability is to increase the connectivity of the underlying MOF network, which necessarily increases material density and reduces porosity. Here we demonstrate an alternative paradigm, whereby elastic stability is enhanced in a MOF with an aperiodic network topology. We use a combination of variable-pressure single-crystal X-ray diffraction measurements and coarse-grained lattice-dynamical calculations to interrogate the high-pressure behaviour of the topologically aperiodic system TRUMOF-1, which we compare against that of its ordered congener MOF-5. We show that the topology of the former quenches the elastic instability responsible for pressure-induced framework collapse in the latter, much as irregularity in the shapes and sizes of stones acts to prevent cooperative mechanical failure in drystone walls. Our results establish aperiodicity as a counterintuitive design motif in engineering the mechanical properties of framework structures, relevant to MOFs and larger-scale architectures alike.

Topological Phase Transitions with Zero Indirect Band Gap. (arXiv:2312.13907v1 [cond-mat.mes-hall])
Giandomenico Palumbo

Topological phase transitions in band models are usually associated to the gap closing between the highest valance band and the lowest conduction band, which can give rise to different types of nodal structures, such as Dirac/Weyl points, lines and surfaces. In this work, we show the existence of a different kind of topological phase transitions in one-dimensional systems, which are instead characterized by the presence of a robust zero indirect gap, which occurs when the top of the valence band coincides with the bottom of the conduction band in energy but not in momentum. More specifically, we consider an one-dimensional model on a diamond-like chain that is protected by both particle-hole and chiral-inversion symmetries. At the critical point, the system supports a Dirac-like point. After introducing a deforming parameter that breaks both inversion and chiral symmetries but preserves their combination, we observe the emergence of a zero indirect band gap, which results to be related to the persymmetry of our Hamiltonian. Importantly, the zero indirect gap holds for a range of values of the deforming parameter. We finally discuss the implementation of the deforming parameter in our tight-binding model through time-periodic (Floquet) driving.

Quantum Transport and Spectroscopy of Two-dimensional Perovskite/Graphene Interfaces. (arXiv:2312.13956v1 [cond-mat.mes-hall])
Yan Sun, C. Morice, D. Garrot, R. Weil, K. Watanabe, T. Taniguchi, M. Monteverde, A.D. Chepelianskii

Quantum transport properties in molecularly thin perovskite/graphene heterostructure are experimentally investigated by Shubnikov-de Hass (SdH) oscillation and photo-resistance spectroscopy. We find an efficient charge transfer between the perovskite nanosheets and graphene, with a high hole concentration in graphene of up to $\rm \sim 2.8 \times 10^{13}\ cm^{-2}$. The perovskite layer also increases Fermi velocity lowering the effective mass of graphene from expected $\rm \sim 0.12\ m_e$ to $\rm \sim 0.08\ m_e$. Combining magneto-resistance and density functional theory calculations, we find that the carrier density in graphene significantly depends on the perovskite termination at the interface, affecting the charge transfer process and leading to a coexistence of regions with different doping. We also investigate the photo-response of the SdH oscillation under illumination. Using photo-resistance spectroscopy, we find evidence of photo-assisted transport across the perovskite layer between two graphene electrodes mediated by hot carriers in perovskite. Our results provide a picture to understand the transport behavior of 2D perovskite/graphene heterostructure and a reference for the controlled design of interfaces in perovskite optoelectronic devices.

Theory of interlayer exciton dynamics in 2D TMDCs Heterolayers under the influence of strain reconstruction and disorder. (arXiv:2312.14054v1 [cond-mat.mes-hall])
Marten Richter

Monolayers of transition metal dichalcogenides (TMDC) became one of the most studied nanostructures in the last decade. Combining two different TMDC monolayers results in a heterostructure whose properties can be individually tuned by the twist angle between the lattices of the two van-der-Waals layers and the relative placement of the layers, leading to Moir\'e cells. For small twist angles, lattice reconstruction leads to strong strain fields in the Moir\'e cells. In this paper, we combine an existing theory for lattice reconstruction with a quantum dynamic theory for interlayer excitons and their dynamics due to exciton phonon scattering using a polaron transformation. The exciton theory is formulated in real space instead of the commonly used quasi-momentum space to account for imperfections in the heterolayer breaking lattice translational symmetry. We can analyze the structure of the localized and delocalized exciton states and their exciton-phonon scattering rates for single phonon processes using Born-Markov approximation and multi-phonon processes using a polaron transformation. Furthermore, linear optical spectra and exciton relaxation Green functions are calculated and discussed.

Pseudo-spectral Landau-Lifshitz description of magnetization dynamics. (arXiv:2312.14068v1 [cond-mat.mes-hall])
Kyle Rockwell, Joel Hirst, Thomas A. Ostler, Ezio Iacocca

Magnetic materials host a wealth of nonlinear dynamics, textures, and topological defects. This is possible due to the competition between strong nonlinearity and dispersion that act at the atomic scale as well as long-range interactions. However, these features are difficult to analytically and numerically study because of the vastly different temporal and spatial scales involved. Here, we present a pseudo-spectral approach for the Landau-Lifshitz equation that invokes energy and momentum conservation embodied in the magnon dispersion relation to accurately describe both atomic and continuum limits. Furthermore, this approach enables analytical study at every scale. We show the applicability of this model in both the continuum and atomic limit by investigating modulational instability and ultrafast evolution of magnetization due to transient grating, respectively, in a 1D ferromagnetic chain with perpendicular magnetic anisotropy. This model provides the possibility of grid-independent multiscale numerical approaches that will enable the description of singularities within a single framework.

Nano-Imaging of Landau-Phonon Polaritons in Dirac Heterostructures. (arXiv:2312.14093v1 [physics.optics])
Lukas Wehmeier, Suheng Xu, Rafael A. Mayer, Brian Vermilyea, Makoto Tsuneto, Michael Dapolito, Rui Pu, Zengyi Du, Xinzhong Chen, Wenjun Zheng, Ran Jing, Zijian Zhou, Kenji Watanabe, Takashi Taniguchi, Adrian Gozar, Qiang Li, Alexey B. Kuzmenko, G. Lawrence Carr, Xu Du, Michael M. Fogler, D.N. Basov, Mengkun Liu

Polaritons are light-matter quasiparticles that govern the optical response of quantum materials and enable their nanophotonic applications. We have studied a new type of polaritons arising in magnetized graphene encapsulated in hexagonal boron nitride (hBN). These polaritons stem from hybridization of Dirac magnetoexciton modes of graphene with waveguide phonon modes of hBN crystals. We refer to these quasiparticles as the Landau-phonon polaritons (LPPs). Using infrared magneto nanoscopy, we imaged LPPs and controlled their real-space propagation by varying the magnetic field. These LLPs have large in-plane momenta and are not bound by the conventional optical selection rules, granting us access to the "forbidden" inter-Landau level transitions (ILTs). We observed avoided crossings in the LPP dispersion - a hallmark of the strong coupling regime - occurring when the magnetoexciton and hBN phonon frequencies matched. Our LPP-based nanoscopy also enabled us to resolve two fundamental many-body effects: the graphene Fermi velocity renormalization and ILT-dependent magnetoexciton binding energies. These results indicate that magnetic-field-tuned Dirac heterostructures are promising platforms for precise nanoscale control and sensing of light-matter interaction.

Phase transitions in intrinsic magnetic topological insulator with high-frequency pumping. (arXiv:2106.02840v5 [cond-mat.mes-hall] UPDATED)
Fang Qin, Rui Chen, Hai-Zhou Lu

In this work, we investigate the topological phase transitions in an effective model for a topological thin film with high-frequency pumping. In particular, our results show that the circularly polarized light can break the time-reversal symmetry and induce the quantum anomalous Hall insulator (QAHI) phase. Meanwhile, the bulk magnetic moment can also break the time-reversal symmetry. Therefore, it shows rich phase diagram by tunning the intensity of the light and the thickness of the thin film. Using the parameters fitted by experimental data, we give the topological phase diagram of the Cr-doped Bi$_{2}$Se$_{3}$ thin film, showing that by modulating the strength of the polarized optical field in an experimentally accessible range, there are four different phases: the normal insulator phase, the time-reversal-symmetry-broken quantum spin Hall insulator phase, and two different QAHI phases with opposite Chern numbers. Comparing with the non-doped Bi$_{2}$Se$_{3}$, it is found that the interplay between the light and bulk magnetic moment separates the two different QAHI phases with opposite Chern numbers. The results show that an intrinsic magnetic topological insulator with high-frequency pumping is an ideal platform for further exploring various topological phenomena with a spontaneously broken time-reversal symmetry.

Robustness of the Floquet-assisted superradiant phase and possible laser operation. (arXiv:2211.01320v2 [cond-mat.other] UPDATED)
Lukas Broers, Ludwig Mathey

We demonstrate the robustness of the recently established Floquet-assisted superradiant phase of the parametrically driven dissipative Dicke model, inspired by light-induced dynamics in graphene. In particular, we show the robustness of this state against key imperfections and argue for the feasibility of utilizing it for laser operation. We consider the effect of a finite linewidth of the driving field, modelled via phase diffusion. We find that the linewidth of the light field in the cavity narrows drastically across the FSP transition, reminiscent of a line narrowing at the laser transition. We then demonstrate that the FSP is robust against inhomogeneous broadening, while displaying a reduction of light intensity. We show that the depleted population inversion of near-resonant Floquet states leads to hole burning in the inhomogeneously broadened Floquet spectra. Finally, we show that the FSP is robust against dissipation processes, with coefficients up to values that are experimentally available. We conclude that the FSP presents a robust mechanism that is capable of realistic laser operation.

Light-induced phase crossovers in a quantum spin Hall system. (arXiv:2211.09114v3 [cond-mat.mes-hall] UPDATED)
Fang Qin, Ching Hua Lee, Rui Chen

In this work, we theoretically investigate the light-induced topological phases and finite-size crossovers in a paradigmatic quantum spin Hall (QSH) system with high-frequency pumping optics. Taking the HgTe quantum well for an example, our numerical results show that circularly polarized light can break time-reversal symmetry and induce the quantum anomalous Hall (QAH) phase. In particular, the coupling between the edge states is spin dependent and is related not only to the size of the system, but also to the strength of the polarized pumping optics. By tuning the two parameters (system width and optical pumping strength), we obtain four transport regimes, namely, QSH, QAH, edge conducting, and normal insulator. These four different transport regimes have contrasting edge conducting properties, which will feature prominently in transport experiments on various topological materials.

Universal bounds on optimization of free energy harvesting. (arXiv:2303.04975v3 [cond-mat.stat-mech] UPDATED)
Jordi Piñero, Ricard Solé, Artemy Kolchinsky

Harvesting free energy from the environment is essential for the operation of many biological and artificial systems. We investigate the maximum rate of harvesting achievable by optimizing a set of reactions in a Markovian system, possibly given topological, kinetic, and thermodynamic constraints. We show that the maximum harvesting rate can be expressed as a variational principle, which we solve in closed-form for three physically meaningful regimes. Our approach is relevant for optimal design and for quantifying efficiency of existing reactions. Our results are illustrated on bacteriorhodopsin, a light-driven proton pump from Archae, which is found to be close to optimal under realistic conditions.

Theoretical insights on structural, electronic and thermoelectric properties of inorganic biphenylene: non-benzenoid Boron nitride. (arXiv:2304.00868v2 [cond-mat.mtrl-sci] UPDATED)
Ajay Kumar, Parbati Senapati, Prakash parida

The first-principles calculations predict a stable biphenylene carbon network (BPN) like the Boron-nitride structure named inorganic biphenylene network (I-BPN). A comparison has been done between BPN and I-BPN to examine the stability of the I-BPN monolayer. We calculate the formation energy, phonon dispersion and mechanical parameters: young modulus and Poisson ratio for mechanical stability. It has been found that the stability of I-BPN is comparable with the BPN. The lattice transport properties reveal that the phonon thermal conductivity of I-BPN is 10th order low than the BPN. The electronic band structure reveals that I-BPN is a semiconductor with an indirect bandgap of 1.88 eV with valence band maximum (VBM) at Y and conduction band maximum (CBM) at the X high symmetry point. In addition, the thermoelectric parameters, such as the seebeck coefficient, show the highest peak value of 0.00292 V/K at 324K. Electronic transport properties reveal that I-BPN is highly anisotropic along the x and y-axes. Furthermore, the thermoelectric power factor as a function of chemical potential shows a peak value of 0.0056 W/mK2 (900K) along the x-axis in the p-type doping region. An electronic figure of merit shows an amplified peak approach to 1. The total figure of merit (including lattice transport parameters) shows peak values of 0.378 (0.21) for p-type and 0.24 (0.198) n-type regions along the x(y) direction. It is notice that the obtain ZT peaks values are higher than any B-N compositions.

Light-induced half-quantized Hall effect and axion insulator. (arXiv:2306.03187v4 [cond-mat.mes-hall] UPDATED)
Fang Qin, Ching Hua Lee, Rui Chen

Motivated by the recent experimental realization of the half-quantized Hall effect phase in a three-dimensional (3D) semi-magnetic topological insulator [M. Mogi et al., Nature Physics 18, 390 (2022)], we propose a scheme for realizing the half-quantized Hall effect and axion insulator in experimentally mature 3D topological insulator heterostructures. Our approach involves optically pumping and/or magnetically doping the topological insulator surface, such as to break time reversal and gap out the Dirac cones. By toggling between left and right circularly polarized optical pumping, the sign of the half-integer Hall conductance from each of the surface Dirac cones can be controlled, such as to yield half-quantized ($0+1/2$), axion ($-1/2+1/2=0$), and Chern ($1/2+1/2=1$) insulator phases. We substantiate our results based on detailed band structure and Berry curvature numerics on the Floquet Hamiltonian in the high-frequency limit. Our paper showcases how topological phases can be obtained through mature experimental approaches such as magnetic layer doping and circularly polarized laser pumping and opens up potential device applications such as a polarization chirality-controlled topological transistor.

Competing mechanisms govern the thermal rectification behavior in semi-stochastic polycrystalline graphene with graded grain-size distribution. (arXiv:2307.12940v3 [cond-mat.mtrl-sci] UPDATED)
Simanta Lahkar, Raghavan Ranganathan

Thermal rectifiers are devices that have different thermal conductivities in opposing directions of heat flow. The realization of practical thermal rectifiers relies significantly on a sound understanding of the underlying mechanisms of asymmetric heat transport, and two-dimensional materials offer a promising opportunity in this regard owing to their simplistic structures together with a vast possibility of tunable imperfections. However, the in-plane thermal rectification mechanisms in 2D materials like graphene having directional gradients of grain sizes have remained elusive. In fact, understanding the heat transport mechanisms in polycrystalline graphene, which are more practical to synthesize than large-scale single-crystal graphene, could potentially allow a unique opportunity, in principle, to combine with other defects and designs for effective optimization of thermal rectification. In this work, we investigate the thermal rectification behavior in periodic atomistic models of polycrystalline graphene whose grain arrangements were generated semi-stochastically to have different gradient grain-density distributions along the in-plane heat flow direction. We employ the centroidal Voronoi tessellation technique to generate realistic grain boundary structures for graphene, and the non-equilibrium molecular dynamics simulations method is used to calculate the thermal conductivities and rectification values. Additionally, detailed phonon characteristics and propagating phonon spatial energy densities are analyzed based on the fluctuation-dissipation theory to elucidate the competitive interplay between two underlying mechanisms, namely, (1) propagating phonon coupling and (2) temperature-dependence of thermal conductivity that determine the degree of asymmetric heat flow in graded polycrystalline graphene.

Fluctuations in the active Dyson Brownian motion and the overdamped Calogero-Moser model. (arXiv:2307.14306v2 [cond-mat.stat-mech] UPDATED)
Leo Touzo, Pierre Le Doussal, Gregory Schehr

Recently, we introduced the active Dyson Brownian motion model (DBM), in which $N$ run-and-tumble particles interact via a logarithmic repulsive potential in the presence of a harmonic well. We found that in a broad range of parameters the density of particles converges at large $N$ to the Wigner semi-circle law, as in the passive case. In this paper, we provide an analytical support for this numerical observation, by studying the fluctuations of the positions of the particles in the nonequilibrium stationary state of the active DBM, in the regime of weak noise and large persistence time. In this limit, we obtain an analytical expression for the covariance between the particle positions for any $N$ from the exact inversion of the Hessian matrix of the system. We show that, when the number of particles is large $N \gg 1$, the covariance matrix takes scaling forms that we compute explicitly both in the bulk and at the edge of the support of the semi-circle. In the bulk, the covariance scales as $N^{-1}$, while at the edge, it scales as $N^{-2/3}$. Remarkably, we find that these results can be transposed directly to an equilibrium model, the overdamped Calogero-Moser model in the low temperature limit, providing an analytical confirmation of the numerical results by Agarwal, Kulkarni and Dhar. For this model, our method also allows us to obtain the equilibrium two-time correlations and their dynamical scaling forms both in the bulk and at the edge. Our predictions at the edge are reminiscent of a recent result in the mathematics literature by Gorin and Kleptsyn on the (passive) DBM. That result can be recovered by the present methods, and also, as we show, using the stochastic Airy operator. Finally, our analytical predictions are confirmed by precise numerical simulations, in a wide range of parameters.

Torsional Force Microscopy of Van der Waals Moir\'es and Atomic Lattices. (arXiv:2308.08814v2 [cond-mat.mtrl-sci] UPDATED)
Mihir Pendharkar, Steven J. Tran, Gregory Zaborski Jr., Joe Finney, Aaron L. Sharpe, Rupini V. Kamat, Sandesh S. Kalantre, Marisa Hocking, Nathan J. Bittner, Kenji Watanabe, Takashi Taniguchi, Bede Pittenger, Christina J. Newcomb, Marc A. Kastner, Andrew J. Mannix, David Goldhaber-Gordon

In a stack of atomically-thin Van der Waals layers, introducing interlayer twist creates a moir\'e superlattice whose period is a function of twist angle. Changes in that twist angle of even hundredths of a degree can dramatically transform the system's electronic properties. Setting a precise and uniform twist angle for a stack remains difficult, hence determining that twist angle and mapping its spatial variation is very important. Techniques have emerged to do this by imaging the moir\'e, but most of these require sophisticated infrastructure, time-consuming sample preparation beyond stack synthesis, or both. In this work, we show that Torsional Force Microscopy (TFM), a scanning probe technique sensitive to dynamic friction, can reveal surface and shallow subsurface structure of Van der Waals stacks on multiple length scales: the moir\'es formed between bi-layers of graphene and between graphene and hexagonal boron nitride (hBN), and also the atomic crystal lattices of graphene and hBN. In TFM, torsional motion of an AFM cantilever is monitored as it is actively driven at a torsional resonance while a feedback loop maintains contact at a set force with the sample surface. TFM works at room temperature in air, with no need for an electrical bias between the tip and the sample, making it applicable to a wide array of samples. It should enable determination of precise structural information including twist angles and strain in moir\'e superlattices and crystallographic orientation of VdW flakes to support predictable moir\'e heterostructure fabrication.

Structural, morphological, and magnetic characterizations of (Fe0.25Mn0.75)2O3 nanocrystals: a comprehensive stoichiometric determination. (arXiv:2308.11128v2 [cond-mat.mtrl-sci] UPDATED)
John C. Mantilla, Luiz C. C. M. Nagamine, Daniel R. Cornejo, Renato Cohen, Wesley de Oliveira, Paulo E. N. Souza, Sebastião W. da Silva, Fermin F.H. Aragón, Pedro L. Gastelois, Paulo C. Morais, José A.H. Coaquira

Iron manganese trioxide (Fe0.25Mn0.75)2O3 nanocrystals were synthesized by the sol-gel method. The 80 K Mossbauer spectrum was well-fitted using two doublets representing the 8b and 24d crystallographic sites of the (FexMn1-x)2O3 phase and two weak extra sextets which were attributed to crystalline and amorphous hematite. Our findings showed formation of a bixbyite primary phase. The Raman spectrum exhibits six Raman active modes, typical of (Fe,Mn)2O3, and two extra Raman modes associated with the secondary hematite phase. X-ray photoelectron spectroscopy analysis confirmed the presence of oxygen vacancy onto the (FexMn1-x)2O3 particle surface, with varying oxidation states. X-band magnetic resonance data revealed a single broad resonance line in the whole temperature range (3.8 K - 300 K). The temperature dependence of both resonance field and resonance linewidth shows a remarkable change in the range of 40 - 50 K, herein credited to surface spin glass behavior. The model picture used assumes (FexMn1-x)2O3 nanoparticles with a core-shell structure. Results indicate that below about 50 K the spin system of shell reveals a paramagnetic to spin glass-like transition upon cooling, with a critical temperature estimated at 43 K. In the higher temperature range, the superparamagnetic hematite (secondary) phase contributes remarkably to the temperature dependence of the resonance linewidth. Zero-field-cooled (ZFC) and fieldcooled (FC) data show strong irreversibility and a peak in the ZFC curve at 33 K, attributed to a paramagnetic-ferrimagnetic transition of the main phase. Hysteresis curve at 5 K shows a low coercive field of 4 kOe, with the magnetization not reaching saturation at 70 kOe, suggesting the occurrence of a ferrimagnetic core with a magnetic disorder at surface, characteristic of core-shell spin-glass-like behavior.

The role of pressure-induced stacking faults on the magnetic properties of gadolinium. (arXiv:2309.01285v3 [cond-mat.mtrl-sci] UPDATED)
Rafael Martinho Vieira, Olle Eriksson, Torbjörn Björkman, Ondřej Šipr, Heike C. Herper

Experimental data show that under pressure, Gd goes through a series of structural transitions hcp to Sm-type (close-packed rhombohedral) to dhcp that is accompanied by a gradual decrease of the Curie temperature and magnetization till the collapse of a finite magnetization close to the dhcp structure. We explore theoretically the pressure-induced changes of the magnetic properties, by describing these structural transitions as the formation of fcc stackings faults. Using this approach, we are able to describe correctly the variation of the Curie temperature with pressure, in contrast to a static structural model using the hcp structure.

Coarse-grained crystal graph neural networks for reticular materials design. (arXiv:2310.19500v2 [cond-mat.mtrl-sci] UPDATED)
Vadim Korolev, Artem Mitrofanov

Reticular materials, including metal-organic frameworks and covalent organic frameworks, combine relative ease of synthesis and an impressive range of applications in various fields, from gas storage to biomedicine. Diverse properties arise from the variation of building units$\unicode{x2013}$metal centers and organic linkers$\unicode{x2013}$in almost infinite chemical space. Such variation substantially complicates experimental design and promotes the use of computational methods. In particular, the most successful artificial intelligence algorithms for predicting properties of reticular materials are atomic-level graph neural networks, which optionally incorporate domain knowledge. Nonetheless, the data-driven inverse design involving these models suffers from incorporation of irrelevant and redundant features such as full atomistic graph and network topology. In this study, we propose a new way of representing materials, aiming to overcome the limitations of existing methods; the message passing is performed on a coarse-grained crystal graph that comprises molecular building units. To highlight the merits of our approach, we assessed predictive performance and energy efficiency of neural networks built on different materials representations, including composition-based and crystal-structure-aware models. Coarse-grained crystal graph neural networks showed decent accuracy at low computational costs, making them a valuable alternative to omnipresent atomic-level algorithms. Moreover, the presented models can be successfully integrated into an inverse materials design pipeline as estimators of the objective function. Overall, the coarse-grained crystal graph framework is aimed at challenging the prevailing atom-centric perspective on reticular materials design.

Theoretical Investigation of the Periodic Anderson Hamiltonian of Samarium Hexaboride. (arXiv:2311.00583v2 [cond-mat.mes-hall] UPDATED)
Partha Goswami, Udai Prakash Tyagi

The periodic Anderson Hamiltonian of the bulk samarium hexaboride is investigated in this article assuming the presence of ferromagnetic impurities (FM). The problem of large on-site electron-electron repulsion is reformulated in terms of a holonomic constraint using slave-boson technique. The model analysis yields the possibility of the quantum anomalous Hall phase albeit with high integer value of the Chern number despite no band-crossing feature at discrete nodes as in 3D (Weyl) systems. Also, upon using the Fu-Kane-Mele formalism, it is shown that the surface Hamiltonian without FM corresponds to a strong topological insulator.

Angular dependence of the interlayer coupling at the interface between two dimensional materials 1T-PtSe$_2$ and graphene. (arXiv:2311.08165v2 [cond-mat.mes-hall] UPDATED)
P. Mallet, F. Ibrahim, K. Abdukayumov, A. Marty, C. Vergnaud, F. Bonell, M. Chshiev, M. Jamet, J-Y. Veuillen

We present a study by Scanning Tunneling Microscopy, supported by ab initio calculations, of the interaction between graphene and monolayer (semiconducting) PtSe$_2$ as a function of the twist angle ${\theta}$ between the two layers. We analyze the PtSe$_2$ contribution to the hybrid interface states that develop within the bandgap of the semiconductor to probe the interaction. The experimental data indicate that the interlayer coupling increases markedly with the value of ${\theta}$, which is confirmed by ab initio calculations. The moir\'e patterns observed within the gap are consistent with a momentum conservation rule between hybridized states, and the strength of the hybridization can be qualitatively described by a perturbative model.

An on-chip platform for multi-degree-of-freedom control of two-dimensional quantum and nonlinear materials. (arXiv:2311.12030v2 [cond-mat.mes-hall] UPDATED)
Haoning Tang, Yiting Wang, Xueqi Ni, Kenji Watanabe, Takashi Taniguchi, Shanhui Fan, Eric Mazur, Amir Yacoby, Yuan Cao

Two-dimensional materials (2DM) and their derived heterostructures have electrical and optical properties that are widely tunable via several approaches, most notably electrostatic gating and interfacial engineering such as twisting. While electrostatic gating is simple and has been ubiquitously employed on 2DM, being able to tailor the interfacial properties in a similar real-time manner represents the next leap in our ability to modulate the underlying physics and build exotic devices with 2DM. However, all existing approaches rely on external machinery such as scanning microscopes, which often limit their scope of applications, and there is currently no means of tuning a 2D interface that has the same accessibility and scalability as electrostatic gating. Here, we demonstrate the first on-chip platform designed for 2D materials with in situ tunable interfacial properties, utilizing a microelectromechanical system (MEMS). Each compact, cost-effective, and versatile device is a standalone micromachine that allows voltage-controlled approaching, twisting, and pressurizing of 2DM with high accuracy. As a demonstration, we engineer synthetic topological singularities, known as merons, in the nonlinear optical susceptibility of twisted hexagonal boron nitride (h-BN), via simultaneous control of twist angle and interlayer separation. The chirality of the resulting moire pattern further induces a strong circular dichroism in the second-harmonic generation. A potential application of this topological nonlinear susceptibility is to create integrated classical and quantum light sources that have widely and real-time tunable polarization. Our invention pushes the boundary of available technologies for manipulating low-dimensional quantum materials, which in turn opens up the gateway for designing future hybrid 2D-3D devices for condensed-matter physics, quantum optics, and beyond.

Correlation between microstructural deformation mechanisms and acoustic parameters on a cold-rolled Cu30Zn brass. (arXiv:2311.14430v2 [cond-mat.mtrl-sci] UPDATED)
Maria Sosa, Linton Carvajal, Vicente Salinas, Fernando Lund, Claudio Aguilar, Felipe Castro

The relationship between acoustic parameters and the microstructure of a Cu30Zn brass plate subjected to plastic deformation was evaluated. The plate, previously annealed at 550 {\deg}C for 30 minutes, was cold rolled to reductions in the 10-70\% range. Using the pulse-echo method, linear ultrasonic measurements were performed on each of the nine specimens, corresponding to the nine different reductions, recording the wave times of flight of longitudinal wave along the thickness axis. Subsequently, acoustic measurements were performed to determine the nonlinear parameter ($\beta$) through the second harmonic generation. X-ray diffraction analysis revealed a steady increase and subsequent saturation of deformation twins at 40\% thickness reduction. At higher deformations, the microstructure revealed the generation and proliferation of shear bands, which coincided with a decrease in the twinning structure and an increase in dislocation density rate. Longitudinal wave velocity exhibited a 0.9\% decrease at 20\% deformation, followed by a continuous increase of 2\% beyond this point. These results can be rationalized as a competition between a proliferation of dislocations, which tends to decrease the linear sound velocity, and a decrease in average grain size, which tends to increase it. These variations are in agreement with the values obtained with XRD, Vickers hardness and metallography measurements. The nonlinear parameter $\beta$ shows a significant maximum, at the factor of 8 level, at 40\% deformation. This maximum correlates well with a similar maximum, at a factor of ten level and also at 40\% deformation, of the twinning fault probability.

Flat bands, strange metals, and the Kondo effect. (arXiv:2312.10659v2 [cond-mat.str-el] UPDATED)
Joseph G. Checkelsky, B. Andrei Bernevig, Piers Coleman, Qimiao Si, Silke Paschen

Flat band materials such as the kagome metals or moir\'e superlattice systems are of intense current interest. Flat bands can result from the electron motion on numerous (special) lattices and usually exhibit topological properties. Their reduced bandwidth proportionally enhances the effect of Coulomb interaction, even when the absolute magnitude of the latter is relatively small. Seemingly unrelated to these cases is the large family of strongly correlated electron systems, which includes the heavy fermion compounds, cuprate and pnictide superconductors. In addition to itinerant electrons from large, strongly overlapping orbitals, they frequently contain electrons from more localized orbitals, which are subject to a large Coulomb interaction. The question then arises as to what commonality in the physical properties and microscopic physics, if any, exists between the two broad categories of materials? A rapidly increasing body of strikingly similar phenomena across the different platforms -- from electronic localization-delocalization transitions to strange metal behavior and unconventional superconductivity -- suggests that similar underlying principles could be at play. Indeed, it has recently been suggested that flat band physics can be understood in terms of Kondo physics. Inversely, the concept of electronic topology from lattice symmetry, which is fundamental in flat band systems, is enriching the field of strongly correlated electron systems where correlation-driven topological phases are increasingly being investigated. Here we elucidate this connection, survey the new opportunities for cross-fertilization in understanding across the platforms, and assess the prospect for new insights that may be gained into both the correlation physics and its intersection with electronic topology.

Found 5 papers in prb
Date of feed: Fri, 22 Dec 2023 04:16:56 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)

${\mathrm{Ti}}_{3}{\mathrm{O}}_{5}$ monolayer: Tunable quantum anomalous Hall insulator
Xiaokang Xu, Tianxia Guo, Donghao Guan, Jie Li, Ailei He, Jinlian Lu, Xiaojing Yao, Yongjun Liu, and Xiuyun Zhang
Author(s): Xiaokang Xu, Tianxia Guo, Donghao Guan, Jie Li, Ailei He, Jinlian Lu, Xiaojing Yao, Yongjun Liu, and Xiuyun Zhang

The quantum anomalous Hall (QAH) effect has attracted significant attention due to its potential applications in low-power-consumption spintronic devices. In this study, we performed density functional theory calculations to investigate the stability, electronic, and topological properties of ${\mat…

[Phys. Rev. B 108, 214427] Published Thu Dec 21, 2023

Competing magnetic fluctuations and orders in a multiorbital model of doped ${\mathrm{SrCo}}_{2}{\mathrm{As}}_{2}$
Ana-Marija Nedić, Morten H. Christensen, Y. Lee, Bing Li, Benjamin G. Ueland, Rafael M. Fernandes, Robert J. McQueeney, Liqin Ke, and Peter P. Orth
Author(s): Ana-Marija Nedić, Morten H. Christensen, Y. Lee, Bing Li, Benjamin G. Ueland, Rafael M. Fernandes, Robert J. McQueeney, Liqin Ke, and Peter P. Orth

We revisit the intriguing magnetic behavior of the paradigmatic itinerant frustrated magnet $\mathrm{Sr}{\mathrm{Co}}_{2}{\mathrm{As}}_{2}$, which shows strong and competing magnetic fluctuations yet does not develop long-range magnetic order. By calculating the static spin susceptibility $χ(\mathbf…

[Phys. Rev. B 108, 245149] Published Thu Dec 21, 2023

Entanglement spectra of nonchiral topological ($2+1$)-dimensional phases with strong time-reversal symmetry breaking, Li-Haldane state counting, and PEPS
Mark J. Arildsen, Norbert Schuch, and Andreas W. W. Ludwig
Author(s): Mark J. Arildsen, Norbert Schuch, and Andreas W. W. Ludwig

The Li-Haldane correspondence [Phys. Rev. Lett. 101, 010504 (2008)] is often used to help identify wave functions of $(2+1)$-dimensional chiral topological phases (i.e., with nonzero chiral central charge) by studying low-lying entanglement spectra (ES) on long cylinders of finite circumference. Her…

[Phys. Rev. B 108, 245150] Published Thu Dec 21, 2023

Quantum confinement and interference via Fabry-Pérot-like resonators in rhombohedral trilayer graphene on graphite
Zi-Yi Han, Lin He, and Long-Jing Yin
Author(s): Zi-Yi Han, Lin He, and Long-Jing Yin

Rhombohedral trilayer graphene (rTG) has recently emerged as a new playground for exploring flatband-induced exotic quantum phenomena and sparked considerable concern. However, the experimental accessing of local quantum behaviors such as the quantum confinement of flatband electrons in rTG has been…

[Phys. Rev. B 108, 245422] Published Thu Dec 21, 2023

Single laser pulse induced magnetization switching in in-plane magnetized GdCo alloys
Jun-Xiao Lin, Michel Hehn, Thomas Hauet, Yi Peng, Junta Igarashi, Yann Le Guen, Quentin Remy, Jon Gorchon, Gregory Malinowski, Stéphane Mangin, and Julius Hohlfeld
Author(s): Jun-Xiao Lin, Michel Hehn, Thomas Hauet, Yi Peng, Junta Igarashi, Yann Le Guen, Quentin Remy, Jon Gorchon, Gregory Malinowski, Stéphane Mangin, and Julius Hohlfeld

The discovery of all-optical ultrafast deterministic magnetization switching has opened up new possibilities for manipulating magnetization in devices using femtosecond laser pulses. Previous studies on single pulse all-optical helicity-independent switching (AO-HIS) have mainly focused on perpendic…

[Phys. Rev. B 108, L220403] Published Thu Dec 21, 2023

Found 2 papers in prl
Date of feed: Fri, 22 Dec 2023 04:16:54 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)

Improved Measurements of Muonic Helium Ground-State Hyperfine Structure at a Near-Zero Magnetic Field
P. Strasser, S. Fukumura, R. Iwai, S. Kanda, S. Kawamura, M. Kitaguchi, S. Nishimura, S. Seo, H. M. Shimizu, K. Shimomura, H. Tada, and H. A. Torii (MuSEUM Collaboration)
Author(s): P. Strasser, S. Fukumura, R. Iwai, S. Kanda, S. Kawamura, M. Kitaguchi, S. Nishimura, S. Seo, H. M. Shimizu, K. Shimomura, H. Tada, and H. A. Torii (MuSEUM Collaboration)

Muonic helium atom hyperfine structure (HFS) measurements are a sensitive tool to test the three-body atomic system and bound-state quantum electrodynamics theory, and determine fundamental constants of the negative muon magnetic moment and mass. The world’s most intense pulsed negative muon beam at…

[Phys. Rev. Lett. 131, 253003] Published Thu Dec 21, 2023

Continuous Phase Transitions between Fractional Quantum Hall States and Symmetry-Protected Topological States
Ying-Hai Wu, Hong-Hao Tu, and Meng Cheng
Author(s): Ying-Hai Wu, Hong-Hao Tu, and Meng Cheng

In Bose-Fermi mixtures under particular conditions, a symmetry-protected topological state goes through a continuous transition to two decoupled fractional quantum Hall states.

[Phys. Rev. Lett. 131, 256502] Published Thu Dec 21, 2023

Found 1 papers in pr_res
Date of feed: Fri, 22 Dec 2023 04:16:54 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)

Ultrafast all-optical manipulation of the charge-density wave in ${\mathrm{VTe}}_{2}$
Manuel Tuniz, Davide Soranzio, Davide Bidoggia, Denny Puntel, Wibke Bronsch, Steven L. Johnson, Maria Peressi, Fulvio Parmigiani, and Federico Cilento
Author(s): Manuel Tuniz, Davide Soranzio, Davide Bidoggia, Denny Puntel, Wibke Bronsch, Steven L. Johnson, Maria Peressi, Fulvio Parmigiani, and Federico Cilento

The charge-density-wave (CDW) phase in the layered transition-metal dichalcogenide ${\mathrm{VTe}}_{2}$ is strongly coupled to the band inversion involving vanadium and tellurium orbitals. In particular, this coupling leads to a selective disappearance of the Dirac-type states that characterize the …

[Phys. Rev. Research 5, 043276] Published Thu Dec 21, 2023

Found 2 papers in nano-lett
Date of feed: Thu, 21 Dec 2023 14:06:53 GMT

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

[ASAP] Free-Standing Carbon Nanotube Embroidered Graphene Film Electrode Array for Stable Neural Interfacing
Lei Gao, Suye Lv, Yuanyuan Shang, Shouliang Guan, Huihui Tian, Ying Fang, Jinfen Wang, and Hongbian Li

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Nano Letters
DOI: 10.1021/acs.nanolett.3c03421

[ASAP] Nanoscale Manipulation of Exciton–Trion Interconversion in a MoSe2 Monolayer via Tip-Enhanced Cavity-Spectroscopy
Mingu Kang, Su Jin Kim, Huitae Joo, Yeonjeong Koo, Hyeongwoo Lee, Hyun Seok Lee, Yung Doug Suh, and Kyoung-Duck Park

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Nano Letters
DOI: 10.1021/acs.nanolett.3c03920

Found 1 papers in acs-nano
Date of feed: Thu, 21 Dec 2023 14:03:07 GMT

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

[ASAP] Vertical Phase-Engineering MoS2 Nanosheet-Enhanced Textiles for Efficient Moisture-Based Energy Generation
Yuan-Ming Cao, Yang Su, Mi Zheng, Peng Luo, Yang-Biao Xue, Bin-Bin Han, Min Zheng, Zuoshan Wang, Liang-Sheng Liao, and Ming-Peng Zhuo

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ACS Nano
DOI: 10.1021/acsnano.3c08132