Found 57 papers in cond-mat
Date of feed: Tue, 08 Aug 2023 00:30:00 GMT

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An Effective Hydrodynamic Description of Marching Locusts. (arXiv:2308.02589v1 [q-bio.QM])
Dan Gorbonos, Felix Oberhauser, Luke L. Costello, Yannick Günzel, Einat Couzin-Fuchs, Benjamin Koger, Iain D. Couzin

A fundamental question in complex systems is how to relate interactions between individual components ("microscopic description") to the global properties of the system ("macroscopic description"). Another fundamental question is whether such a macroscopic description exists at all and how well it describes the large-scale properties. Here, we address these questions using as a canonical example of a self-organizing complex system - the collective motion of desert locusts. One of the world's most devastating insect plagues begins when flightless juvenile locusts form "marching bands". Moving through semiarid habitats in the search for food, these bands display remarkable coordinated motion. We investigated how well physical models can describe the flow of locusts within a band. For this, we filmed locusts within marching bands during an outbreak in Kenya and automatically tracked all individuals passing through the camera frame. We first analysed the spatial topology of nearest neighbors and found individuals to be isotropically distributed. Despite this apparent randomness, a local order was observed in regions of high density with a clear second neighbor peak in the radial distribution function, akin to an ordered fluid. Furthermore, reconstructing individual locust trajectories revealed a highly-aligned movement, consistent with the one-dimensional version of the Toner-Tu equations, which are a generalization of the Navier-Stokes equations for fluids, used to describe the equivalent macroscopic fluid properties of active particles. Using this effective Toner-Tu equation, which relates the gradient of the pressure to the acceleration, we show that the effective "pressure" of locusts increases as a linear function of density in segments with highest polarization. Our study thus demonstrates an effective hydrodynamic description of flow dynamics in plague locust swarms.


Nature of even and odd magic angles in helical twisted trilayer graphene. (arXiv:2308.02638v1 [cond-mat.mes-hall])
Daniele Guerci, Yuncheng Mao, Christophe Mora

Helical twisted trilayer graphene exhibits zero-energy flat bands with large degeneracy in the chiral limit. The flat bands emerge at a discrete set of magic twist angles and feature properties intrinsically distinct from those realized in twisted bilayer graphene. Their degeneracy and the associated band Chern numbers depend on the parity of the magic angles. Two degenerate flat bands with Chern numbers $C_A=2$ and $C_B=-1$ arise at odd magic angles, whereas even magic angles display four flat bands, with Chern number $C_{A/B}=\pm1$, together with a Dirac cone crossing at zero energy. All bands are sublattice polarized. We demonstrate the structure behind these flat bands and obtain analytical expressions for the wavefunctions in all cases. Each magic angle is identified with the vanishing of a zero-mode wavefunction at high-symmetry position and momentum. The whole analytical structure results from whether the vanishing is linear or quadratic for the, respectively, odd and even magic angle. The $C_{3z}$ and $C_{2y}T$ symmetries are shown to play a key role in establishing the flat bands. In contrast, the particle-hole symmetry is not essential, except from gapping out the crossing Dirac cone at even magic angles.


Observation of Fractionally Quantized Anomalous Hall Effect. (arXiv:2308.02657v1 [cond-mat.mes-hall])
Heonjoon Park, Jiaqi Cai, Eric Anderson, Yinong Zhang, Jiayi Zhu, Xiaoyu Liu, Chong Wang, William Holtzmann, Chaowei Hu, Zhaoyu Liu, Takashi Taniguchi, Kenji Watanabe, Jiun-haw Chu, Ting Cao, Liang Fu, Wang Yao, Cui-Zu Chang, David Cobden, Di Xiao, Xiaodong Xu

The integer quantum anomalous Hall (QAH) effect is a lattice analog of the quantum Hall effect at zero magnetic field. This striking transport phenomenon occurs in electronic systems with topologically nontrivial bands and spontaneous time-reversal symmetry breaking. Discovery of its putative fractional counterpart in the presence of strong electron correlations, i.e., the fractional quantum anomalous Hall (FQAH) effect, would open a new chapter in condensed matter physics. Here, we report the direct observation of both integer and fractional QAH effects in electrical measurements on twisted bilayer MoTe$_2$. At zero magnetic field, near filling factor $\nu = -1$ (one hole per moir\'e unit cell) we see an extended integer QAH plateau in the Hall resistance $R_\text{xy}$ that is quantized to $h/e^2 \pm 0.1 \%$ while the longitudinal resistance $R_\text{xx}$ vanishes. Remarkably, at $\nu=-2/3$ and $-3/5$ we see plateau features in $R_\text{xy}$ at $3h/2e^2 \pm 1\%$ and $5h/3e^2 \pm 3\%$, respectively, while $R_\text{xx}$ remains small. All these features shift linearly in an applied magnetic field with slopes matching the corresponding Chern numbers $-1$, $-2/3$, and $-3/5$, precisely as expected for integer and fractional QAH states. In addition, at zero magnetic field, $R_\text{xy}$ is approximately $2h/e^2$ near half filling ($\nu = -1/2$) and varies linearly as $\nu$ is tuned. This behavior resembles that of the composite Fermi liquid in the half-filled lowest Landau level of a two-dimensional electron gas at high magnetic field. Direct observation of the FQAH and associated effects paves the way for researching charge fractionalization and anyonic statistics at zero magnetic field.


Nonlinear wave propagation in large extra spatial dimensions and the blackbody thermal laws. (arXiv:2308.02685v1 [hep-th])
I. Soares, R. Turcati, S. B. Duarte

The nonlinear wave propagation in large extra spatial dimensions (on and above $d=2$) is investigated in the context of nonlinear electrodynamics theories that depends exclusively on the invariant $\mathcal{F}$. In this vein, we consider propagating waves under the influence of external uniform electric and magnetic fields. Features related to the blackbody radiation in the presence of a background constant electric field such as the generalization of the spectral energy density distribution and the Stefan-Boltzmann law are obtained. Interestingly enough, anisotropic contributions to the frequency spectrum appear in connection to the nonlinearity of the electromagnetic field. In addition, the long wavelength regime and the Wien's displacement law in this situation are studied. The corresponding thermodynamics quantities at thermal equilibrium, such as energy, pressure, entropy and heat capacity densities are contemplated as well.


Screened plasmons of graphene near a perfect electric conductor. (arXiv:2308.02691v1 [physics.optics])
Afshin Moradi, Nurhan Turker Tokan

Screened plasmon properties of graphene near a perfect electric conductor are investigated using classical electrodynamics and a linearized hydrodynamic model that includes Fermi correction. A general expression for the dispersion relation of the mentioned screened plasmonic waves is given and illustrated graphically. The result indicates that for realistic wavenumbers, the dispersion relation of plasmonic waves of isolated graphene is almost unaffected by the Fermi correction, while this correction is an important factor for the screened plasmons of graphene near a perfect electric conductor, where it increases the frequency of surface waves. The results show that near the graphene neutrality point, the surface wave has a linear dispersion with a universal speed close to $v_{\mathrm{F}}/\sqrt{2}$. Such linear dispersion for surface waves (also known as energy waves) appears to be a common occurrence when a splitting of plasma frequencies occurs, e.g. in the electron-hole plasma of graphene [W. Zhao \textit{et al}., Nature \textbf{614}, 688 (2023)]. Furthermore, analytical expressions for the energy parameters (the power flow, energy density, and energy velocity) of screened plasmons of the system are derived. Also, the analytical expressions are derived and analyzed for the damping function and surface plasmon and electromagnetic field strength functions of surface waves of the system with small intrinsic damping.


The role of Coulomb interaction on the electronic properties of monolayer NiX$_2$ (X = S, Se): A DFT+U+V study. (arXiv:2308.02737v1 [cond-mat.mes-hall])
Sergio Bravo, P.A. Orellana, L. Rosales

The electronic structure of Nickel dichalcogenides, NiS$_2$ and NiSe$_2$, in monolayer form, is studied employing first-principles methods. We assess the importance of band ordering, covalency and Coulomb interactions in the ground state of these systems. Hybrid functional results are compared with standard functionals and also with Hubbard-corrected functionals to systematically address the role of electronic interactions and localization. We found that mean-field correlation realized by intersite Hubbard interactions are directly linked to the magnitude of the energy band gap, giving compelling evidence for the presence of a charge transfer insulating phase in these materials.


Probing charge order of monolayer NbSe$_2$ within a bulk crystal. (arXiv:2308.02772v1 [cond-mat.mtrl-sci])
Doron Azoury, Edoardo Baldini, Aravind Devarakonda, Jiarui Li, Shiang Fang, Pheona Williams, Riccardo Comin, Joseph Checkelsky, Nuh Gedik

Atomically thin transition metal dichalcogenides can exhibit markedly different electronic properties compared to their bulk counterparts. In the case of NbSe$_2$, the question of whether its charge density wave (CDW) phase is enhanced in the monolayer limit has been the subject of intense debate, primarily due to the difficulty of decoupling this order from its environment. Here, we address this challenge by using a misfit crystal that comprises NbSe$_2$ monolayers separated by SnSe rock-salt spacers, a structure that allows us to investigate a monolayer crystal embedded in a bulk matrix. We establish an effective monolayer electronic behavior of the misfit crystal by studying its transport properties and visualizing its electronic structure by angle-resolved photoemission measurements. We then investigate the emergence of the CDW by tracking the temperature dependence of its collective modes. Our findings reveal a nearly sixfold enhancement in the CDW transition temperature, providing compelling evidence for the profound impact of dimensionality on charge order formation in NbSe$_2$.


Quasiparticle and Transport Properties of Disordered Bilayer Graphene. (arXiv:2308.02779v1 [cond-mat.dis-nn])
Yanru Chen, Bo Fu, Jinrong Xu, Qinwei Shi, Ping Cui, Zhenyu Zhang

In recent experimental and theoretical studies of graphene, disorder scattering processes have been suggested to play an important role in its electronic and transport properties. In the preceding paper, it has been shown that the nonperturbative momentum-space Lanczos method is able to accurately describe all the multiple impurity scattering events and account for the quasiparticle and transport properties of disordered monolayer graphene. In the present study, we expand the range of applicability of this recursive method by numerically investigating the quasiparticle and transport properties of Bernal-stacked bilayer graphene in the presence of scalar Anderson disorder. The results are further compared with the findings of the same system using a self-consistent Born approximation, as well as the central findings in the preceding paper for monolayer graphene. It is found that in both systems, proper inclusions of all the scattering events are needed in order to reliably capture the role of disorder via multiple impurity scattering. In particular, the quasiparticle residue is shown to decrease sharply near the charge neutrality point, suggesting that the system is either a marginal Fermi liquid or a non-Fermi liquid. Furthermore, we reveal the dependences of the transport properties of disordered bilayer graphene on the carrier density and temperature, and explore the role of interlayer scattering at varying strengths. Our findings help to provide some new angles into the quasiparticle and transport properties of disordered bilayer graphene.


Shape-dependent friction scaling laws in twisted layered material interfaces. (arXiv:2308.02818v1 [physics.app-ph])
Weidong Yan, Xiang Gao, Wengen Ouyang, Ze Liu, Oded Hod, Michael Urbakh

Static friction induced by moir\'e superstructure in twisted incommensurate finite layered material interfaces reveals unique double periodicity and lack of scaling with contact size. The underlying mechanism involves compensation of incomplete moir\'e tiles at the rim of rigid polygonal graphene flakes sliding atop fixed graphene or h-BN substrates. The scaling of friction (or lack thereof) with contact size is found to strongly depend on the shape of the slider and the relative orientation between its edges and the emerging superstructure, partially rationalizing scattered experimental data. With careful consideration of the flake edge orientation, twist angle, and sliding direction along the substrate, one should therefore be able to achieve large-scale superlubricity via shape tailoring.


Fractional quantum Hall effect in valley-layer locked Landau levels in bilayer MoS$_{2}$. (arXiv:2308.02821v1 [cond-mat.mes-hall])
Siwen Zhao, Jinqiang Huang, Valentin Crépel, Xingguang Wu, Tongyao Zhang, Hanwen Wang, Xiangyan Han, Zhengyu Li, Chuanying Xi, Senyang Pan, Zhaosheng Wang, Kenji Watanabe, Takashi Taniguchi, Benjamin Sacépé, Jing Zhang, Ning Wang, Jianming Lu, Nicolas Regnault, Zheng Vitto Han

Semiconducting transition-metal dichalcogenides (TMDs) exhibit high mobility, strong spin-orbit coupling, and large effective masses, which simultaneously leads to a rich wealth of Landau quantizations and inherently strong electronic interactions. However, in spite of their extensively explored Landau levels (LL) structure, probing electron correlations in the fractionally filled LL regime has not been possible due to the difficulty of reaching the quantum limit. Here, we report evidence for fractional quantum Hall (FQH) states at filling fractions 4/5 and 2/5 in the lowest LL of bilayer MoS$_{2}$, manifested in fractionally quantized transverse conductance plateaus accompanied by longitudinal resistance minima. We further show that the observed FQH states result from and sensitively depend on the dielectric and gate screening of the Coulomb interactions. Our findings establish a new FQH experimental platform which are a scarce resource: it is tunable by Coulomb-screening engineering and as such, is the missing link between atomically thin graphene and semiconducting quantum wells.


Nonequilibrium thermodynamic signatures of collective dynamical states around chimera in a chemical reaction network. (arXiv:2308.02857v1 [cond-mat.stat-mech])
Premashis Kumar, Gautam Gangopadhyay

Different dynamical states ranging from coherent, incoherent to chimera, multichimera, and related transitions are addressed in a globally coupled nonlinear continuum chemical oscillator system by implementing a modified complex Ginzburg-Landau equation. Besides dynamical identifications of observed states using standard qualitative metrics, we systematically acquire nonequilibrium thermodynamic characterizations of these states obtained via coupling parameters. The nonconservative work profiles in collective dynamics qualitatively reflect the time-integrated concentration of the activator, and the majority of the nonconservative work contributes to the entropy production over the spatial dimension. It is illustrated that the evolution of spatial entropy production and semigrand Gibbs free energy profiles associated with each state are connected yet completely out of phase, and these thermodynamic signatures are extensively elaborated to shed light on the exclusiveness and similarities of these states. Moreover, a relationship between the proper nonequilibrium thermodynamic potential and the variance of activator concentration is established by exhibiting both quantitative and qualitative similarities between a Fano factor-like entity, derived from the activator concentration, and the Kullback-Leibler divergence associated with the transition from a nonequilibrium homogeneous state to an inhomogeneous state. Quantifying the thermodynamic costs for collective dynamical states would aid in efficiently controlling, manipulating, and sustaining such states to explore the real-world relevance and applications of these states.


A powered full quantum eigensolver for energy band structures. (arXiv:2308.03134v1 [cond-mat.mtrl-sci])
Bozhi Wang, Jingwei Wen, Jiawei Wu, Haonan Xie, Fan Yang, Shijie Wei, Gui-lu Long

There has been an increasing research focus on quantum algorithms for condensed matter systems recently, particularly on calculating energy band structures. Here, we propose a quantum algorithm, the powered full quantum eigensolver(P-FQE), by using the exponentiation of operators of the full quantum eigensolver(FQE). This leads to an exponential increase in the success probability of measuring the target state in certain circumstances where the number of generating elements involved in the exponentiation of operators exhibit a log polynomial dependence on the number of orbitals. Furthermore, we conduct numerical calculations for band structure determination of the twisted double-layer graphene. We experimentally demonstrate the feasibility and robustness of the P-FQE algorithm using superconducting quantum computers for graphene and Weyl semimetal. One significant advantage of our algorithm is its ability to reduce the requirements of extremely high-performance hardware, making it more suitable for energy spectra determination on noisy intermediate-scale quantum (NISQ) devices.


Magic Angles and Fractional Chern Insulators in Twisted Homobilayer TMDs. (arXiv:2308.03143v1 [cond-mat.str-el])
Nicolás Morales-Durán, Nemin Wei, Allan H. MacDonald

We explain the appearance of magic angle flat bands and fractional Chern insulators in twisted K-valley homobilayer transition metal dichalcogenides by mapping their continuum model to a Landau level problem. Our approach relies on an adiabatic approximation for the quantum mechanics of valence band holes in a layer-pseudospin field that is valid for sufficiently small twist angles and on a lowest Landau level approximation that is valid for sufficiently large twist angles. It simply explains why the quantum geometry of the lowest moir\'e miniband is close to ideal at the flat-band twist angle, predicts that flat bands occur only when the valley-dependent moir\'e potential is sufficiently strong compared to the interlayer tunneling amplitude, and provides a powerful starting point for the study of interactions.


Core-shell nanocrystals for plasmon-enhanced photodetection in the graphene-based hybrid photodetector. (arXiv:2308.03167v1 [cond-mat.mtrl-sci])
Anima Ghosh, Shyam Narayan Singh Yadav, Ming-Hsiu Tsai, Abhishek Dubey, Shangjr Gwo, Chih-Ting Lin, Ta- Jen Yen

Incorporating plasmonic metal nanostructures into the semiconductor compounds in the form of core-shell offers a new route to improving the performance of photodetectors. Herein, we have reported the development of a high-performance photodetector based on Cu2NiSnS4 (CNTS) nanocrystals (NCs) and Au/CNTS core-shell structures (complex or others, instead NC), for the first time, as a proof-of-concept experiment using the colloidal hot-injection method. The photoactive Au/CNTS core-shell NCs exhibit enhanced optical absorption, carrier extraction efficiency, and improved photo-sensing performance. It is depicted that using this Au/CNTS core-shell/graphene-based photodetector, there is a significant increment in optoelectronic responses compared to using a pristine CNTS/graphene-based photodetector. The maximum responsivity, detectivity, and external quantum efficiency (EQE) of 1.2 $\times 10^{3}$ AW$^{-1}$, 6.2$\times 10^{11}$ Jones, and 3.8$\times 10^{5}$ \% were measured at an illumination power density of 318.5 $\mu$Wcm-2. Importantly, this enhanced optoelectronic performance is mainly due to the plasmonic-induced resonance energy transfer (PIRET) effect of core Au; carrier density is significantly increased between the Au core and CNTS shell. Further, the device using Au/CNTS exhibits a fast response/recovery time of 2.58/11.14 sec and excellent operational reliability. These results enlighten a new era in the fabrication and development of plasmonic core-shell nanostructures-based visible photo-sensing devices for imaging applications.


Breakdown of Chiral Edge Modes in Topological Magnon Insulators. (arXiv:2308.03168v1 [cond-mat.str-el])
Jonas Habel (1 and 2), Alexander Mook (3 and 1), Josef Willsher (1 and 2), Johannes Knolle (1 and 2 and 4) ((1) Technical University of Munich, (2) Munich Center for Quantum Science and Technology, (3) Johannes Gutenberg-University Mainz, (4) Blackett Laboratory London)

Topological magnon insulators (TMI) are ordered magnets supporting chiral edge magnon excitations. These edge states are envisioned to serve as topologically protected information channels in low-loss magnonic devices. The standard description of TMI is based on linear spin-wave theory (LSWT), which approximates magnons as free non-interacting particles. However, magnon excitations of TMI are genuinely interacting even at zero temperature, calling into question descriptions based on LSWT alone. Here we perform a detailed non-linear spin-wave analysis to investigate the stability of chiral edge magnons. We identify three general breakdown mechanisms: (1) The edge magnon couples to itself, generating a finite lifetime that can be large enough to lead to a spectral annihilation of the chiral state; (2) The edge magnon hybridizes with the extended bulk magnons and, as a consequence, delocalizes away from the edge; (3) Due to a bulk-magnon mediated edge-to-edge coupling, the chiral magnons at opposite edges hybridize. We argue that, in general, these breakdown mechanisms may invalidate predictions based on LSWT and violate the notion of topological protection. We discuss strategies how the breakdown of chiral edge magnons can be avoided, e.g. via the application of large magnetic fields. Our results highlight a challenge for the realization of chiral edge states in TMI and in other bosonic topological systems without particle number conservation.


Terahertz chiral metamaterial cavities breaking time-reversal symmetry. (arXiv:2308.03195v1 [cond-mat.mes-hall])
Johan Andberger, Lorenzo Graziotto, Luca Sacchi, Mattias Beck, Giacomo Scalari, Jérôme Faist

We demonstrate terahertz chiral metamaterial cavities that break time-reversal symmetry by coupling the degenerate linearly polarized modes of two orthogonal sets of nano-antenna arrays using the inter-Landau level transition of a two-dimensional electron gas in a perpendicular magnetic field, realizing normalized light-matter coupling rates up to $\Omega_R/\omega_{\mathrm{cav}} = 0.78$. The deep sub-wavelength confinement and gap of the nano-antennas means that the ultra-strong coupling regime can be reached even with a very small number of carriers, making it viable to be used with a variety of 2D materials, including graphene. In addition it possesses a non-degenerate chiral ground state that can be used to study the effect of circularly polarized electromagnetic quantum fluctuations by means of weakly-perturbing magneto-transport measurements.


Quadrupolar Excitons and Hybridized Interlayer Mott Insulator in a Trilayer Moir\'e Superlattice. (arXiv:2308.03219v1 [cond-mat.mes-hall])
Zhen Lian, Dongxue Chen, Lei Ma, Yuze Meng, Ying Su, Li Yan, Xiong Huang, Qiran Wu, Xinyue Chen, Mark Blei, Takashi Taniguchi, Kenji Watanabe, Sefaattin Tongay, Chuanwei Zhang, Yong-Tao Cui, Su-Fei Shi

Transition metal dichalcogenide (TMDC) moir\'e superlattices, owing to the moir\'e flatbands and strong correlation, can host periodic electron crystals and fascinating correlated physics. The TMDC heterojunctions in the type-II alignment also enable long-lived interlayer excitons that are promising for correlated bosonic states, while the interaction is dictated by the asymmetry of the heterojunction. Here we demonstrate a new excitonic state, quadrupolar exciton, in a symmetric WSe2-WS2-WSe2 trilayer moir\'e superlattice. The quadrupolar excitons exhibit a quadratic dependence on the electric field, distinctively different from the linear Stark shift of the dipolar excitons in heterobilayers. This quadrupolar exciton stems from the hybridization of WSe2 valence moir\'e flatbands. The same mechanism also gives rise to an interlayer Mott insulator state, in which the two WSe2 layers share one hole laterally confined in one moir\'e unit cell. In contrast, the hole occupation probability in each layer can be continuously tuned via an out-of-plane electric field, reaching 100% in the top or bottom WSe2 under a large electric field, accompanying the transition from quadrupolar excitons to dipolar excitons. Our work demonstrates a trilayer moir\'e system as a new exciting playground for realizing novel correlated states and engineering quantum phase transitions.


Hydrogen Transport Between Layers of Transition Metal-Dichalcogenides. (arXiv:2308.03418v1 [cond-mat.mtrl-sci])
Ismail Eren, Yun An, Agnieszka B. Kuc

Hydrogen is a crucial source of green energy and has been extensively studied for its potential usage in fuel cells. The advent of two-dimensional crystals (2DCs) has taken hydrogen research to new heights, enabling it to tunnel through layers of 2DCs or be transported within voids between the layers, as demonstrated in recent experiments by Geim's group. In this study, we investigate how the composition and stacking of transition-metal dichalcogenide (TMDC) layers influence the transport and self-diffusion coefficients (D) of hydrogen atoms using well-tempered metadynamics simulations. Our findings show that modifying either the transition metal or the chalcogen atoms significantly affects the free energy barriers (Delta F) and, consequently, the self-diffusion of hydrogen atoms between the 2DC layers. In the Hh polytype (2H stacking), MoSe2 exhibits the lowest Delta F, while WS2 has the highest, resulting in the largest D for the former system. Additionally, hydrogen atoms inside the RhM (or 3R) polytype encounter more than twice lower energy barriers and, thus, much higher diffusivity compared to those within the most stable Hh stacking. These findings are particularly significant when investigating twisted layers or homo- or heterostructures, as different stacking areas may dominate over others, potentially leading to directional transport and interesting materials for ion or atom sieving.


How to enhance anomalous Hall effects in magnetic Weyl semimetal Co$_3$Sn$_2$S$_2$?. (arXiv:2308.03483v1 [cond-mat.mtrl-sci])
Shivam Rathod, Megha Malasi, Archana Lakhani, Devendra Kumar

Large spin-orbit coupling, kagome lattice, nontrivial topological band structure with inverted bands anti-crossings, and Weyl nodes are essential ingredients, ideally required to obtain maximal anomalous Hall effect (AHE) are simultaneously present in Co$_3$Sn$_2$S$_2$. It is a leading platform to show large intrinsic anomalous Hall conductivity (AHC) and giant anomalous Hall angle (AHA) simultaneously at low fields. The giant AHE in Co$_3$Sn$_2$S$_2$ is robust against small-scale doping-related chemical potential changes. In this work, we unveil a selective and co-chemical doping route to maximize AHEs in Co$_3$Sn$_2$S$_2$. To begin with, in Co$_3$Sn$_{2-x}$In$_x$S$_2$, we brought the chemical potential at the hotspot of Berry curvature along with a maximum of asymmetric impurity scattering in high mobility region. As a result at x=0.05, we found a significant enhancement of AHA (95%) and AHC (190%) from the synergistic enhancement of extrinsic and intrinsic mechanisms from modified Berry curvature of gaped nodal lines. Later, with anticipation of further improvements in AHE, we grew hole-co-doped Co$_{3-y}$Fe$_y$Sn$_{2-x}$In$_x$S$_2$ crystals, where we found rather a suppression of AHEs. The role of dopants in giving extrinsic effects or band broadening can be better understood when chemical potential does not change after doping. By simultaneous and equal co-doping with electrons and holes in Co$_{3-y-z}$Fe$_y$Ni$_z$Sn$_2$S$_2$, we kept the chemical potential unchanged. Henceforth, we found a significant enhancement in intrinsic AHC $\sim$116% due to the disorder broadenings in kagome bands


Abelian and non-Abelian quantum spin liquids in a three-component Bose gas on optical Kagome lattices. (arXiv:2308.03509v1 [cond-mat.quant-gas])
Kaiye Shi, Wei Zhang, Zheng-Xin Liu

Realization of non-Abelian anyons in topological phases is a crucial step toward topological quantum computation. We propose a scheme to realize a non-Abelian quantum spin liquid (QSL) phase in a three-component Bose gas with contact interaction on optical Kagome lattices. In the strong coupling regime, the system is described by an effective spin-1 model with two- and three-body interactions between neighboring spins. By mapping out the phase diagram via variational Monte Carlo method, we find a non-Abelian chiral spin liquid phase in which the Ising-type anyons obey non-Abelian braiding statistics. The gapless chiral edge states can be detected by measuring the spin-spin correlation from atomic population. Furthermore, an interesting Z2 QSL phase is observed exhibiting both topological order and lattice symmetry breaking order. Our scheme can be implemented in cold quantum gases of bosonic atoms.


Fusion Mechanism for Quasiparticles and Topological Quantum Order in the Lowest-Landau-Level. (arXiv:2308.03548v1 [cond-mat.str-el])
Arkadiusz Bochniak, Gerardo Ortiz

Starting from Halperin multilayer systems we develop a hierarchical scheme that generates, bosonic and fermionic, single-layer quantum Hall states (or vacua) of arbitrary filling factor. Our scheme allows for the insertion of quasiparticle excitations with either Abelian or non-Abelian statistics and quantum numbers that depend on the nature of the original vacuum. Most importantly, it reveals a fusion mechanism for quasielectrons and magnetoexcitons that generalizes ideas about particle fractionalization introduced in Commun. Phys. 5, 171 (2022) for the case of Laughlin fluids. In addition, in the second quantization representation, we uncover the inherent topological quantum order characterizing these vacua. In particular, we illustrate the methodology by constructing generalized composite (generalized Read) operators for the non-Abelian Pfaffian and Hafnian quantum fluid states.


Phase separation in tilings of a bounded region of the plane. (arXiv:2308.03552v1 [cond-mat.stat-mech])
Eduardo J. Aguilar, Valmir C. Barbosa, Raul Donangelo, Sergio R. Souza

Given a finite set of two-dimensional tile types, the field concerned with covering the plane with tiles of these types only has a long history, having enjoyed great prominence in the last six to seven decades, not only as a topic of recreational mathematics but mainly as a topic of scientific interest. Much of this interest has revolved around fundamental geometrical problems such as minimizing the variety of tile types to be used, and also around important applications in areas such as crystallography and others concerned with various atomic- and molecular-scale phenomena. All applications are of course confined to finite regions, but in many cases they refer back directly to progress in tiling the whole plane. Tilings of bounded regions of the plane have also been actively studied, but in general the additional complications imposed by the boundary conditions tend to constrain progress to mostly indirect results, such as recurrence relations. Here we study the tiling of rectangular regions of the plane by squares, dominoes, and straight tetraminoes. For this set of tile types, not even recurrence relations seem to be available. Our approach is to seek to characterize this system through some of the fundamental quantities of statistical physics. We do this on two parallel tracks, one fully analytical for a special case, the other based on the Wang-Landau method for state-density estimation. Given a simple Hamiltonian based solely on tile contacts, we have found either approach to lead to illuminating depictions of entropy, temperature, and above all phase separation. The notion of phase separation, in this context, refers to keeping track of how many tiles of each type are used in each of the many possibilities. We have found that this helps bind together different aspects of the system in question and conjecture that future applications will benefit from the possibilities it affords.


Tuning the initial phase to control the final state of a driven qubit: single-passage coherent destruction of tunneling. (arXiv:2308.03571v1 [quant-ph])
Polina Kofman, Sergey Shevchenko, Franco Nori

A driven quantum system can experience Landau-Zener-Stueckelberg-Majorana (LZSM) transitions between its states, when the respective energy levels quasi-cross. If this quasicrossing is passed repeatedly under periodic driving, the trajectories can interfere either constructively or destructively. In the latter case, known as coherent destruction of tunneling, the transition between the energy states is suppressed. Even for a double-passage case, the accumulated phase difference (also referred to as the Stueckelberg phase) can lead to destructive interference, resulting in no transition. In this paper we discuss a similar process for a single-passage dynamics. We study the LZSM single-passage problem starting from a superposition state. The phase difference of this initial state results in interference. When this is destructive, resulting in a zero transition probability, such situation can be called single-passage coherent destruction of tunneling. When the phase is chosen so that the occupation probabilities do not change after the transition, this can be called occupation conservation and this is analogous to the problem of transitionless driving. We demonstrate how varying the system parameters (driving velocity, initial phase, initial detuning) can be used for quantum control.


Detection of nontrivial topology driven by charge density wave in a semi-Dirac metal. (arXiv:2308.03587v1 [cond-mat.mtrl-sci])
Rafiqul Alam#, Prasun Boyal1, Shubhankar Roy, Ratnadwip Singha, Buddhadeb Pal, Riju Pal, Prabhat Mandal, Priya Mahadevan, Atindra Nath Pal

The presence of electron correlations in a system with topological order can lead to exotic ground states. Considering single crystals of LaAgSb2 which has a square net crystal structure, one finds multiple charge density wave transitions (CDW) as the temperature is lowered. We find large planar Hall (PHE) signals in the CDW phase, which are still finite in the high temperature phase though they change sign. Optimising the structure within first-principles calculations, one finds an unusual chiral metallic phase. This is because as the temperature is lowered, the separation between the Ag/Sb atoms on different layers decreases, leading to stronger repulsions between electrons associated with atoms on different layers. This leads to successive layers sliding with respect to each other, thereby stabilising a chiral structure in which inversion symmetry is also broken. The large Berry curvature associated with the low-temperature structure explains the low temperature PHE. At high temperature, the PHE arises from the changes induced in the anisotropic Dirac cone in presence a magnetic field. Our work represents a route towards detecting and understanding the mechanism in a correlation driven topological transition through electron transport measurements, complemented by ab-initio electronic structure calculations.


Single crystal growth and characterization of antiferromagnetically ordering EuIn$_2$. (arXiv:2308.03600v1 [cond-mat.mtrl-sci])
Brinda Kuthanazhi, Simon X. M. Riberolles, Dominic H. Ryan, Philip J. Ryan, Jong-Woo Kim, Lin-Lin Wang, Robert J. McQueeney, Benjamin G. Ueland, Paul C. Canfield

We report the single crystal growth and characterization of EuIn$_2$, a magnetic topological semimetal candidate according to our density functional theory (DFT) calculations. We present results from electrical resistance, magnetization, M\"ossbauer spectroscopy, and X-ray resonant magnetic scattering (XRMS) measurements. We observe three magnetic transitions at $T_{\text{N}1}\sim 14.2~$K, $T_{\text{N}2}\sim12.8~$K and $T_{\text{N}3}\sim 11~$K, signatures of which are consistently seen in anisotropic temperature dependent magnetic susceptibility and electrical resistance data. M\"ossbauer spectroscopy measurements on ground crystals suggest an incommensurate sinusoidally modulated magnetic structure below the transition at $T_{\text{N}1}\sim 14~$K, followed by the appearance of higher harmonics in the modulation on further cooling roughly below $T_{\text{N}2}\sim13~$K, before the moment distribution squaring up below the lowest transition around $T_{\text{N}3}\sim 11~$K. XRMS measurements showed the appearance of magnetic Bragg peaks below $T_{\text{N}1}\sim14~$K, with a propagation vector of $\bm{\tau}$ $=(\tau_h,\bar{\tau}_h,0)$, with $\tau_h$varying with temperature, and showing a jump at $T_{\text{N}3}\sim11$~K. The temperature dependence of $\tau_h$ between $\sim11$~K and $14$~K shows incommensurate values consistent with the M\"{o}ssbauer data. XRMS data indicate that $\tau_h$ remains incommensurate at low temperatures and locks into $\tau_h=0.3443(1)$.


Half-quantum flux in spin-triplet superconducting rings with bias current. (arXiv:2308.03668v1 [cond-mat.supr-con])
Kazushi Aoyama

Effects of a bias electric current have been theoretically investigated in a spin-triplet superconducting ring in a magnetic field. Based on the Ginzburg-Landau theory, we show that the bias current can stabilize a half-quantum-flux (HQF) state via couplings to the Zeeman field and the dipole-type spin-orbit interaction, the latter becoming active when the field is tilted from the ring axis. The emergence of the HQF state is reflected as a field-induced half-quantum-shift in the Little-Parks (LP) oscillation in the critical current. Possible relevance to recent LP experiments is also discussed.


Analytic density of states of two-dimensional Chern insulator. (arXiv:2308.03681v1 [cond-mat.str-el])
Vera Uzunova, Krzysztof Byczuk

We present analytic expressions for the density of states and its consistent derivation for the two-dimensional Qi-Wu-Zhang (QWZ) Hamiltonian, a generic model for the Chern topological insulators of class A. This density of states is expressed in terms of elliptical integrals. We discuss and plot special cases of the dispersion relations and the corresponding densities of states. Spectral moments are also presented. The exact formulae ought to be useful in determining physical properties of the non-interacting Chern insulators and within the dynamical mean-field theory for interacting fermions with the QWZ Hamiltonian in the non-interacting limit.


Half-valley Ohmic Contact and Contact-Limited Valley-Contrasting Current Injection. (arXiv:2308.03700v1 [cond-mat.mes-hall])
Xukun Feng, Shi-Jun Liang, Chit Siong Lau, Ching Hua Lee, Shengyuan A. Yang, Yee Sin Ang

Two-dimensional (2D) ferrovalley semiconductor (FVSC) with spontaneous valley polarization offers an exciting material platform for probing Berry phase physics. How FVSC can be incorporated in valleytronic device applications, however, remain an open question. Here we generalize the concept of metal/semiconductor (MS) contact into the realm of valleytronics. We propose the concept of half-valley Ohmic contact in FVSC/graphene heterostructures where the two valleys of FVSC separately forms Ohmic and Schottky contacts with the those of graphene, thus allowing current to be valley-selectively injected through the `Ohmic' valley while being blocked in the `Schottky' valley. We develop a theory of \emph{contact-limited valley-contrasting current injection} and demonstrate such transport mechanism can produce gate-tunable valley-polarized injection current across a FVSC/graphene contact. Using RuCl$_2$/graphene heterostructure as a proof of concept, we illustrate a device concept of valleytronic barristor in whcih high valley polarization efficiency, accompanied by a sizable current on/off ratio, can be achieved under experimentally achievable electrostatic gating conditions. These findings uncover contact-limited valley-contrasting current injection as an efficient mechanism for valley polarization manipulation, and reveals the potential of valleytronic MS contact as a functional building block of valleytronic device technology.


Inhomogeneous high temperature melting and decoupling of charge density waves in spin-triplet superconductor UTe2. (arXiv:2308.03721v1 [cond-mat.supr-con])
Alexander LaFleur, Hong Li, Corey E. Frank, Muxian Xu, Siyu Cheng, Ziqiang Wang, Nicholas P. Butch, Ilija Zeljkovic

Periodic spatial modulations of the superfluid density, or pair density waves, have now been widely detected in unconventional superconductors, either as the primary or the secondary states accompanying charge density waves. Understanding how these density waves emerge, or conversely get suppressed by external parameters, provides an important insight into their nature. Here we use spectroscopic imaging scanning tunneling microscopy to study the evolution of density waves in the heavy fermion spin-triplet superconductor UTe2 as a function of temperature and magnetic field. We discover that charge modulations, composed of three different wave vectors gradually weaken but persist to a surprisingly high temperature T_CDW ~ 10-12 K. By tracking the local amplitude of modulations, we find that these modulations become spatially inhomogeneous, and form patches that shrink in size with higher temperature or with applied magnetic field. Interestingly, one of the density wave vectors along the mirror symmetry has a slightly different temperature onset, thus revealing an unexpected decoupling of the three-component CDW state. Importantly, T_CDW determined from our work matches closely to the temperature scale believed to be related to magnetic fluctuations, providing the first possible connection between density waves observed by surface probes and bulk measurements. Combined with magnetic field sensitivity of the modulations, this could point towards an important role of spin fluctuations or short-range magnetic order in the formation of the primary charge density wave.


Tight-binding models for SG 143 (P3) and application to recent DFT results on copper-doped lead apatite. (arXiv:2308.03751v1 [cond-mat.mes-hall])
Moritz M. Hirschmann, Johannes Mitscherling

Recent density-functional theory (DFT) calculations on copper-doped lead apatite $\text{Pb}_9\text{Cu}(\text{PO}_4)_6\text{O}$ indicated various interesting band structure properties in the close vicinity to the Fermi surface including symmetry-enforced band crossings, narrow bands, and van-Hove singularities. These studies assume a regular arrangement of the dopant, such that the space group (SG) 176 (P6$\text{}_3$/m) is reduced to SG 143 (P3). We construct tight-binding models for this space group with two and four bands. A first analysis of these models show excellent agreement with the key features of the DFT results. We show that the symmetry enforced band crossings at $\Gamma$ and $A$ are double Weyl points, implying Chern bands for $k_z\neq 0,\pi$. We map out the distribution of Berry curvature and quantum metric and discuss their relation to the orbital character. For a specific set of parameters we find a singular flat band.


Interaction-induced charge pumping in a topological many-body system. (arXiv:2308.03756v1 [cond-mat.quant-gas])
Konrad Viebahn, Anne-Sophie Walter, Eric Bertok, Zijie Zhu, Marius Gächter, Armando A. Aligia, Fabian Heidrich-Meisner, Tilman Esslinger

A topological 'Thouless' pump represents the quantised motion of particles in response to a slow, cyclic modulation of external control parameters. The Thouless pump, like the quantum Hall effect, is of fundamental interest in physics because it links physically measurable quantities, such as particle currents, to geometric properties of the experimental system, which can be robust against perturbations and thus technologically useful. So far, experiments probing the interplay between topology and inter-particle interactions have remained relatively scarce. Here we observe a Thouless-type charge pump in which the particle current and its directionality inherently rely on the presence of strong interactions. Experimentally, we utilise fermionic atoms in a dynamical superlattice which traces a pump trajectory that remains trivial in the non-interacting limit. Remarkably, the transferred charge in the interacting system is half of its usual value in the non-interacting case, in agreement with matrix-product-state simulations. Our experiments suggest that Thouless charge pumps are promising platforms to gain insights into interaction-driven topological transitions and topological quantum matter.


Interplay between magnetism and band topology in Kagome magnets $R$Mn$_6$Sn$_6$. (arXiv:2201.11265v3 [cond-mat.mtrl-sci] UPDATED)
Y. Lee, R. Skomski, X. Wang, P. P. Orth, Y. Ren, Byungkyun Kang, A. K. Pathak, A. Kutepov, B. N. Harmon, R. J. McQueeney, I. I. Mazin, Liqin Ke

Kagome-lattice magnets $R$Mn$_6$Sn$_6$ recently emerged as a new platform to exploit the interplay between magnetism and topological electronic states. Some of the most exciting features of this family are the dramatic dependence of the easy magnetization direction on the rare-earth specie and the kagome geometry of the Mn planes that in principle can generate flat bands and Dirac points; gapping of the Dirac points by spin-orbit coupling has been suggested recently to be responsible for the observed anomalous Hall response in the member TbMn$_6$Sn$_6$. In this paper, we address both issues with ab initio calculations. We have discovered the significant role played by higher-order crystal-field parameters and rare-earth magnetic anisotropy constants in these systems. We demonstrate that the microscopic origin of rare-earth anisotropy can also be quantified and understood at various levels: ab initio, phenomenological, and analytical. In particular, using a simple and physically transparent analytical model, we explain, with full quantitative agreement, the evolution of anisotropy across the series. We analyze the topological properties of Mn-dominated bands and demonstrate how they emerge from the multiorbital planar kagome model. We further show that the most pronounced quasi-2D dispersion are too far removed from the Fermi level, and therefore cannot explain the observed quasi-2D anomalous Hall effect. By employing ab initio many-body approaches, we demonstrate that the exchange-correlation effects for itinerant Mn-$d$ electrons do not significantly alter the obtained electronic and magnetic structure. Therefore, we conclude that, contrary to previous claims, the most pronounced 2D kagome-derived topological band features bear little relevance to transport in $R$Mn$_6$Sn$_6$, albeit they may possibly be brought to focus by electron or hole doping.


Unidirectional coherent quasiparticles in the high-temperature rotational symmetry broken phase of AV3Sb5 kagome superconductors. (arXiv:2203.15057v2 [cond-mat.str-el] UPDATED)
Hong Li, He Zhao, Brenden Ortiz, Yuzki Oey, Ziqiang Wang, Stephen D. Wilson, Ilija Zeljkovic

Kagome metals AV3Sb5 (where the A can stand for K, Cs, or Rb) display a rich phase diagram of correlated electron states, including superconductivity and density waves. Within this landscape, recent experiments revealed signs of a transition below approximately 35 K attributed to an electronic nematic phase that spontaneously breaks rotational symmetry of the lattice. Here, we show that rotational symmetry breaking initiates universally at a high temperature in these materials, toward the 2 x 2 charge density wave transition temperature. We do this via spectroscopic-imaging scanning tunneling microscopy and study atomic-scale signatures of electronic symmetry breaking across several materials in the AV3Sb5 family: CsV3Sb5, KV3Sb5 and Sn-doped CsV3Sb5. Below a significantly lower temperature of about 30 K, we measure quantum interference of quasiparticles, a key signature for the formation of a coherent electronic state. These quasiparticles display a pronounced unidirectional feature in reciprocal space that strengthens as the superconducting state is approached. Our experiments reveal that high-temperature rotation symmetry breaking and the charge ordering states are separated from the superconducting ground state by an intermediate-temperature regime with coherent unidirectional quasiparticles. This picture is phenomenologically different compared to that in high-temperature superconductors, shedding light on the complex nature of rotation symmetry breaking in AV3Sb5 kagome superconductors.


Superconductivity induced by gate-driven hydrogen intercalation in the charge-density-wave compound 1T-TiSe2. (arXiv:2205.12951v4 [cond-mat.supr-con] UPDATED)
Erik Piatti, Giacomo Prando, Martina Meinero, Cesare Tresca, Marina Putti, Stefano Roddaro, Gianrico Lamura, Toni Shiroka, Pietro Carretta, Gianni Profeta, Dario Daghero, Renato S. Gonnelli

Hydrogen (H) plays a key role in the near-to-room temperature superconductivity of hydrides at megabar pressures. This suggests that H doping could have similar effects on the electronic and phononic spectra of materials at ambient pressure as well. Here, we demonstrate the non-volatile control of the electronic ground state of titanium diselenide (1T-TiSe$_2$) via ionic liquid gating-driven H intercalation. This protonation induces a superconducting phase, observed together with a charge-density wave through most of the phase diagram, with nearly doping-independent transition temperatures. The H-induced superconducting phase is possibly gapless-like and multi-band in nature, in contrast with those induced in TiSe$_2$ via copper, lithium, and electrostatic doping. This unique behavior is supported by ab initio calculations showing that high concentrations of H dopants induce a full reconstruction of the bandstructure, although with little coupling between electrons and high-frequency H phonons. Our findings provide a promising approach for engineering the ground state of transition metal dichalcogenides and other layered materials via gate-controlled protonation.


Evidence for Exciton Crystals in a 2D Semiconductor Heterotrilayer. (arXiv:2207.09601v3 [cond-mat.mes-hall] UPDATED)
Yusong Bai, Yiliu Li, Song Liu, Yinjie Guo, Jordan Pack, Jue Wang, Cory R. Dean, James Hone, X.-Y. Zhu

Two-dimensional (2D) transition metal dichalcogenides (TMDC) and their moir\'e interfaces have been demonstrated for correlated electron states, including Mott insulators and electron/hole crystals commensurate with moir\'e superlattices. Here we present spectroscopic evidences for ordered bosons - interlayer exciton crystals in a WSe2/MoSe2/WSe2 trilayer, where the enhanced Coulomb interactions over those in heterobilayers have been predicted to result in exciton ordering. While the dipolar interlayer excitons in the heterobilayer may be ordered by the periodic moir\'e traps, their mutual repulsion results in de-trapping at exciton density n_ex larger than 10^11 cm^-2 to form mobile exciton gases and further to electron-hole plasmas, both accompanied by broadening in photoluminescence (PL) peaks and large increases in mobility. In contrast, ordered interlayer excitons in the trilayer are characterized by negligible mobility and by sharper PL peaks persisting to n_ex approximately 10^12 cm^-2. We present evidences for the predicted quadrupolar exciton crystal and its transitions to dipolar excitons either with increasing n_ex or by an applied electric field. These ordered interlayer excitons may serve as models for the exploration of quantum phase transitions and quantum coherent phenomena.


Anomalies in fluid dynamics: flows in a chiral background via variational principle. (arXiv:2207.10195v2 [hep-th] UPDATED)
Alexander G. Abanov, Paul B. Wiegmann

We study flows of barotropic perfect fluid under the simultaneous action of the electromagnetic field and the axial-vector potential, the external field conjugate to the fluid helicity. We obtain the deformation of the Euler equation by the axial-vector potential and the deformations of various currents by two external fields. We show that the divergence of the vector and axial currents are controlled by the chiral anomaly known in quantum field theories with Dirac fermions. We obtain these results by extending the variational principle for barotropic flows of a perfect fluid by coupling with the external axial-vector potential.


Ensnarled: On the topological linkage of spatially embedded network pairs. (arXiv:2208.11662v2 [q-bio.TO] UPDATED)
Felix Kramer, Carl D Modes

The observation, design and analysis of mesh-like networks in bionics, polymer physics and biological systems has brought forward an extensive catalog of fascinating structures of which a subgroup share a particular, yet critically under appreciated attribute: being embedded in space such that one wouldn't be able to pull them apart without prior removal of a subset of edges, a state which we here call ensnarled. In this study we elaborate on a graph theoretical method to analyze ensnarled finite, 2-component nets on the basis of Hopf-link identification. Doing so we are able to construct an edge priority operator, derived from the linking numbers of the spatial graphs' cycle bases, which highlights critical edges. On its basis we developed a greedy algorithm which identifies optimal edge removals to achieve unlinking, allowing for the establishment of a new topological metric characterizing the state of ensnarled network pairs.


Quantum Monte Carlo Study of Semiconductor Artificial Graphene Nanostructures. (arXiv:2210.14696v2 [cond-mat.mes-hall] UPDATED)
Gökhan Öztarhan, E. Bulut Kul, Emre Okcu, A. D. Güçlü

Semiconductor artificial graphene nanostructures where Hubbard model parameter $U/t$ can be of the order of 100, provide a highly controllable platform to study strongly correlated quantum many-particle phases. We use accurate variational and diffusion Monte Carlo methods to demonstrate a transition from antiferromagnetic to metallic phases for experimentally accessible lattice constant $a=50$ nm in terms of lattice site radius $\rho$, for finite sized artificial honeycomb structures containing up to 114 electrons. By analysing spin-spin correlation functions, we show that edge type, geometry and charge nonuniformity affect the steepness and the crossover $\rho$ value of the phase transition. For triangular structures, the metal-insulator transition is accompanied with a smoother edge polarization transition.


Evidence of $\phi$0-Josephson junction from skewed diffraction patterns in Sn-InSb nanowires. (arXiv:2212.00199v2 [cond-mat.mes-hall] UPDATED)
B. Zhang, Z. Li, V. Aguilar, P. Zhang, M. Pendharkar, C. Dempsey, J. S. Lee, S. D. Harrington, S. Tan, J. S. Meyer, M. Houzet, C. J. Palmstrom, S. M. Frolov

We study Josephson junctions based on InSb nanowires with Sn shells. We observe skewed critical current diffraction patterns: the maxima in forward and reverse current bias are at different magnetic flux, with a displacement of 20-40 mT. The skew is greatest when the external field is nearly perpendicular to the nanowire, in the substrate plane. This orientation suggests that spin-orbit interaction plays a role. We develop a phenomenological model and perform tight-binding calculations, both methods reproducing the essential features of the experiment. The effect modeled is the $\phi$0-Josephson junction with higher-order Josephson harmonics. The system is of interest for Majorana studies: the effects are either precursor to or concomitant with topological superconductivity. Current-phase relations that lack inversion symmetry can also be used to design quantum circuits with engineered nonlinearity.


Cataloging topological phases of $N$-stacked Su-Schrieffer-Heeger chains by a systematic breaking of symmetries. (arXiv:2212.02095v2 [cond-mat.str-el] UPDATED)
Aayushi Agrawal, Jayendra N. Bandyopadhyay

Two-dimensional (2D) model of a weak topological insulator with $N$-stacked Su-Schrieffer-Heeger (SSH) chain is studied. This study starts with a basic model with all the fundamental symmetries (chiral, time-reversal, and particle-hole) preserved. Different topological phases are introduced in this model by systematically breaking the system's symmetries. The symmetries are broken by introducing different bonds (hopping terms) in the system. First, the chiral symmetry is broken by introducing hopping within each sub-lattice or intra-sub-lattice hopping, where the hopping strengths of the sub-lattices are equal in magnitudes but opposite in sign. Then, following Haldane, the time-reversal (TR) symmetry is broken by replacing the real intra-sub-lattice hopping strengths with imaginary numbers without changing the magnitudes. We find that breaking chiral and TR symmetries are essential for the weak topological insulator to be a Chern insulator. These models exhibit nontrivial topology with the Chern number $C = \pm 1$. The preservation of the particle-hole (PH) symmetry in the system facilitates an analytical calculation of $C$, which agrees with the numerically observed topological phase transition in the system. An interesting class of topologically nontrivial systems with $C=0$ is also observed, where the non-triviality is identified by quantized and fractional 2D Zak phase. Finally, the PH symmetry is broken in the system by introducing unequal amplitudes of intra-sub-lattice hopping strengths, while the equal intra-sub-lattice hopping strengths ensures the preservation of the inversion symmetry. We investigate the interplay of the PH and the inversion symmetries in the topological phase transition. A discussion on the possible experimental realizations of this model is also presented.


Solving local constraint conditions in slave particle theory. (arXiv:2212.13734v3 [cond-mat.str-el] UPDATED)
Xi Luo, Jianqiao Liu, Yue Yu

With the Becchi-Rouet-Stora-Tyutin (BRST) quantization of gauge theory, we solve the long-standing difficult problem of the local constraint conditions, i.e., the single occupation of a slave particle per site, in the slave particle theory. This difficulty is actually caused by inconsistently dealing with the local Lagrange multiplier $\lambda_i$ which ensures the constraint: In the Hamiltonian formalism of the theory, $\lambda_i$ is time-independent and commutes with the Hamiltonian while in the Lagrangian formalism, $\lambda_i(t)$ becomes time-dependent and plays a role of gauge field. This implies that the redundant degrees of freedom of $\lambda_i(t)$ are introduced and must be removed by the additional constraint, the gauge fixing condition $\partial_t \lambda_i(t)=0$. In literature, this gauge fixing condition was missed. We add this gauge fixing condition and use the BRST quantization of gauge theory for Dirac's first-class constraints in the slave particle theory. This gauge fixing condition endows $\lambda_i(t)$ with dynamics and leads to important physical results. As an example, we study the Hubbard model at half-filling and find that the spinon is gapped in the weak $U$ and the system is indeed a conventional metal, which resolves the paradox that the weak coupling state is a superconductor in the previous slave boson mean field theory. For the $t$-$J$ model, we find that the dynamic effect of $\lambda_i(t)$ substantially suppresses the $d$-wave pairing gap and then the superconducting critical temperature may be lowered at least a factor of one-fifth of the mean field value which is of the order of 1000 K. The renormalized $T_c$ is then close to that in cuprates.


Extended linear-in-$T$ resistivity due to electron-phason scattering in moir\'e superlattices. (arXiv:2302.00043v2 [cond-mat.mes-hall] UPDATED)
Héctor Ochoa, Rafael M. Fernandes

Due to its incommensurate nature, moir\'e superlattices host not only acoustic phonons but also another type of soft collective modes called phasons. Here, we investigate the impact of electron-phason scattering on the transport properties of moir\'e systems. We show that the resistivity can scale linearly with temperature down to temperatures much lower than the Bloch-Gr\"uneisen scale defined by electron kinematics on the Fermi surface. This result stems from the friction between layers, which transfers phason spectral weight to a broad diffusive low-energy peak in the mechanical response of the system. As a result, phason scattering becomes a very efficient channel for entropy production at low temperatures. We also consider the contributions of phasons to thermodynamic properties at low temperatures and find a ''metallic-like'' linear-in-$T$ behavior for the specific heat, despite the fact that this behavior is due to mechanical and not electronic degrees of freedom. We discuss the implications of this finding to reports of linear-in-$T$ resistivity in the phase diagram of twisted bilayer graphene.


A topological mechanism for robust and efficient global oscillations in biological networks. (arXiv:2302.11503v2 [physics.bio-ph] UPDATED)
Chongbin Zheng, Evelyn Tang

Long and stable timescales are often observed in complex biochemical networks, such as in emergent oscillations. How these robust dynamics persist remains unclear, given the many stochastic reactions and shorter time scales demonstrated by underlying components. We propose a topological model with parsimonious parameters that produces long oscillations around the network boundary, effectively reducing the system dynamics to a lower-dimensional current. Using this to model KaiC, which regulates the circadian rhythm in cyanobacteria, we compare the coherence of oscillations to that in other KaiC models. Our topological model localizes currents on the system edge for an efficient regime with simultaneously increased precision and decreased cost. Further, we introduce a new predictor of coherence from the analysis of spectral gaps, and show that our model saturates a global thermodynamic bound. Our work presents a new mechanism for emergent oscillations in complex biological networks utilizing dissipative cycles to achieve robustness and efficient performance.


Non-equilibrium fractional Josephson effect. (arXiv:2303.14385v2 [cond-mat.supr-con] UPDATED)
Aritra Lahiri, Sang-Jun Choi, Björn Trauzettel

Josephson tunnel junctions exhibit a supercurrent typically proportional to the sine of the superconducting phase difference $\phi$. In general, a term proportional to $\cos(\phi)$ is also present, alongside microscopic electronic retardation effects. We show that voltage pulses sharply varying in time prompt a significant impact of the $\cos(\phi)$ term. Its interplay with the $\sin(\phi)$ term results in a non-equilibrium fractional Josephson effect (NFJE) $\sim\sin(\phi/2)$ in the presence of bound states close to zero frequency. Our microscopic analysis reveals that the interference of non-equilibrium virtual quasiparticle excitations is responsible for this phenomenon. We also analyse this phenomenon for topological Josephson junctions with Majorana bound states. Remarkably, the NFJE is independent of the ground state fermion parity unlike its equilibrium counterpart.


Engineering anomalous Floquet Majorana modes and their time evolution in helical Shiba chain. (arXiv:2304.02352v2 [cond-mat.mes-hall] UPDATED)
Debashish Mondal, Arnob Kumar Ghosh, Tanay Nag, Arijit Saha

We theoretically explore the Floquet generation of Majorana end modes~(MEMs) (both regular $0$- and anomalous $\pi$-modes) implementing a periodic sinusoidal modulation in chemical potential in an experimentally feasible setup based on a one-dimensional chain of magnetic impurity atoms having spin spiral configuration (out-of-plane N\'eel-type) fabricated on the surface of most common bulk $s$-wave superconductor. We obtain a rich phase diagram in the parameter space, highlighting the possibility of generating multiple $0$-/$\pi$-MEMs localized at the end of the chain. We also study the real-time evolution of these emergent MEMs, especially when they start to appear in the time domain. These MEMs are topologically characterized by employing the dynamical winding number. We observe that the existing perturbative analysis is unable to explain the numerical findings, indicating the complex mechanism behind the formation of the Floquet Shiba minigap, which is characteristically distinct from other setup e.g. Rashba nanowire model. We also discuss the possible experimental parameters in connection to our model. Our work paves the way to realize the Floquet MEMs in a magnet-superconductor heterostructure.


Generalization of Benalcazar-Bernevig-Hughes model to arbitrary dimensions. (arXiv:2304.07714v2 [cond-mat.mes-hall] UPDATED)
Xun-Jiang Luo, Fengcheng Wu

The Benalcazar-Bernevig-Hughes (BBH) model [Science 357, 61 (2017)], featuring bulk quadrupole moment, edge dipole moments, and corner states, is a paradigm of both higher-order topological insulators and topological multipole insulators. In this work, we generalize the BBH model to arbitrary dimensions and demonstrate the bulk multipole moment. In our demonstration, the analytical solution of corner states can be directly constructed, which possesses a unified and elegant form. Based on the corner states solution and chiral symmetries analysis, we develop a general boundary projection method to extract the boundary Hamiltonians, which thoroughly reveals the boundary-localized multipole moments of lower dimension, the hallmark of topological multipole insulators. Our work facilitates the unified understanding of topological multipole insulators and unveils their cascade hierarchy versatilely.


Gate-defined topological Josephson junctions in Bernal bilayer graphene. (arXiv:2304.11807v2 [cond-mat.mes-hall] UPDATED)
Ying-Ming Xie, Étienne Lantagne-Hurtubise, Andrea F. Young, Stevan Nadj-Perge, Jason Alicea

Recent experiments on Bernal bilayer graphene (BLG) deposited on monolayer WSe$_2$ revealed robust, ultra-clean superconductivity coexisting with sizable induced spin-orbit coupling. Here we propose BLG/WSe$_2$ as a platform to engineer gate-defined planar topological Josephson junctions, where the normal and superconducting regions descend from a common material. More precisely, we show that if superconductivity in BLG/WSe$_2$ is gapped and emerges from a parent state with inter-valley coherence, then Majorana zero modes can form in the barrier region upon applying weak in-plane magnetic fields. Our results spotlight a potential pathway for `internally engineered' topological superconductivity that minimizes detrimental disorder and orbital-magnetic-field effects.


Evidence for chiral supercurrent in quantum Hall Josephson junctions. (arXiv:2305.01766v2 [cond-mat.mes-hall] UPDATED)
Hadrien Vignaud, David Perconte, Wenmin Yang, Bilal Kousar, Edouard Wagner, Frédéric Gay, Kenji Watanabe, Takashi Taniguchi, Hervé Courtois, Zheng Han, Hermann Sellier, Benjamin Sacépé

Hybridizing superconductivity with the quantum Hall (QH) effects has major potential for designing novel circuits capable of inducing and manipulating non-Abelian states for topological quantum computation. However, despite recent experimental progress towards this hybridization, concrete evidence for a chiral QH Josephson junction -- the elemental building block for coherent superconducting-QH circuits -- is still lacking. Its expected signature is an unusual chiral supercurrent flowing in QH edge channels, which oscillates with a specific $2\phi_0$ magnetic flux periodicity ($\phi_0=h/2e$ is the superconducting flux quantum, $h$ the Planck constant and $e$ the electron charge). Here, we show that ultra-narrow Josephson junctions defined in encapsulated graphene nanoribbons exhibit such a chiral supercurrent, visible up to 8 teslas, and carried by the spin-degenerate edge channel of the QH plateau of resistance $h/2e^2\simeq 12.9$ k$\Omega$. We observe reproducible $2\phi_0$-periodic oscillation of the supercurrent, which emerges at constant filling factor when the area of the loop formed by the QH edge channel is constant, within a magnetic-length correction that we resolve in the data. Furthermore, by varying the junction geometry, we show that reducing the superconductor/normal interface length is pivotal to obtain a measurable supercurrent on QH plateaus, in agreement with theories predicting dephasing along the superconducting interface. Our findings mark a critical milestone along the path to explore correlated and fractional QH-based superconducting devices that should host non-Abelian Majorana and parafermion zero modes.


High-Resolution Scanning Tunneling Microscope and its Adaptation for Local Thermopower Measurements in 2D Materials. (arXiv:2305.03418v2 [cond-mat.mtrl-sci] UPDATED)
Jose D. Bermúdez-Perez, Edwin Herrera-Vasco, Javier Casas-Salgado, Hector A. Castelblanco, Karen Vega-Bustos, Gabriel Cardenas-Chirivi, Oscar L. Herrera-Sandoval, Hermann Suderow, Paula Giraldo-Gallo, Jose A. Galvis

We present the design, fabrication and discuss the performance of a new combined high-resolution Scanning Tunneling and thermopower Microscope (STM/SThEM). We also describe the development of the electronic control, the user interface, the vacuum system, and arrangements to reduce acoustical noise and vibrations. We demonstrate the microscope performance with atomic-resolution topographic images of Highly oriented pyrolytic graphite (HOPG) and local thermopower measurements in the semimetal Bi2Te3 sample. Our system offers a tool to investigate the relationship between electronic structure and thermoelectric properties at the nanoscale.


Decay rates of almost strong modes in Floquet spin chains beyond Fermi's Golden Rule. (arXiv:2305.04980v2 [cond-mat.str-el] UPDATED)
Hsiu-Chung Yeh, Achim Rosch, Aditi Mitra

The stability and dynamics of almost strong zero and $\pi$ modes in weakly non-integrable Floquet spin chains are investigated. Such modes can also be viewed as localized Majorana modes at the edge of a topological superconductor. Perturbation theory in the strength of integrability-breaking interaction $J_z$ is employed to estimate the decay rates of these modes, and compared to decay rates obtained from exact diagonalization. The structure of the perturbation theory and thus the lifetime of the modes is governed by the conservation of quasi-energy modulo $2 \pi/T$, where $T$ is the period of the Floquet system. If the quasi-energies of minimally $4 n-1$ quasi-particles adds up to zero (or $\pi/T$ for a $\pi$ mode), the lifetime is proportional to $1/J_z^{2 n}$. Thus the lifetime is sensitively controlled by the width of the single-particle Floquet bands. For regimes where the decay rates are quadratic in $J_z$, an analytic expression for the decay rate in terms of an infinite temperature autocorrelation function of the integrable model is derived, and shown to agree well with exact diagonalization.


Detecting, distinguishing, and spatiotemporally tracking photogenerated charge and heat at the nanoscale. (arXiv:2305.13676v2 [cond-mat.mtrl-sci] UPDATED)
Hannah L. Weaver, Cora M. Went, Joeson Wong, Dipti Jasrasaria, Eran Rabani, Harry A. Atwater, Naomi S. Ginsberg

Since dissipative processes are ubiquitous in semiconductors, characterizing how electronic and thermal energy transduce and transport at the nanoscale is vital for understanding and leveraging their fundamental properties. For example, in low-dimensional transition metal dichalcogenides (TMDCs), excess heat generation upon photoexcitation is difficult to avoid since even with modest injected exciton densities, exciton-exciton annihilation still occurs. Both heat and photoexcited electronic species imprint transient changes in the optical response of a semiconductor, yet the unique signatures of each are difficult to disentangle in typical spectra due to overlapping resonances. In response, we employ stroboscopic optical scattering microscopy (stroboSCAT) to simultaneously map both heat and exciton populations in few-layer \ch{MoS2} on relevant nanometer and picosecond length- and time scales and with 100-mK temperature sensitivity. We discern excitonic contributions to the signal from heat by combining observations close to and far from exciton resonances, characterizing photoinduced dynamics for each. Our approach is general and can be applied to any electronic material, including thermoelectrics, where heat and electronic observables spatially interplay, and lays the groundwork for direct and quantitative discernment of different types of coexisting energy without recourse to complex models or underlying assumptions.


Boundary criticality via gauging finite subgroups: a case study on the clock model. (arXiv:2306.02976v3 [cond-mat.str-el] UPDATED)
Lei Su

Gauging a finite Abelian normal subgroup $\Gamma$ of a nonanomalous 0-form symmetry $G$ of a theory in $(d+1)$D spacetime can yield an unconventional critical point if the original theory has a continuous transition where $\Gamma$ is completely spontaneously broken and if $G$ is a nontrivial extension of $G/\Gamma$ by $\Gamma$. The gauged theory has symmetry $G/\Gamma \times \hat{\Gamma}^{(d-1)}$, where $\hat{\Gamma}^{(d-1)}$ is the $(d-1)$-form dual symmetry of $\Gamma$, and a 't Hooft anomaly between them. Thus it can be viewed as a boundary of a topological phase protected by $G/\Gamma \times \hat{\Gamma}^{(d-1)}$. The ordinary critical point, upon gauging, is mapped to a deconfined quantum critical point between two ordinary symmetry-breaking phases ($d =1$) or an unconventional quantum critical point between an ordinary symmetry-breaking phase and a topologically ordered phase ($d\ge 2$) associated with $G/\Gamma$ and $\hat{\Gamma}^{(d-1)}$, respectively. Order parameters and disorder parameters, before and after gauging, can be directly related. As a concrete example, we gauge the $\mathbb{Z}_2$ subgroup of $\mathbb{Z}_4$ symmetry of a 4-state clock model on a 1D lattice and a 2D square lattice. Since the symmetry of the clock model contains $D_8$, the dihedral group of order 8, we also analyze the anomaly structure which is similar to that in the compactified $SU(2)$ gauge theory with $\theta =\pi$ in $(3+1)$D and its mixed gauge theory. The general case is also discussed.


Weyl Nodes of Opposite Chirality in Ferromagnetic WSM. (arXiv:2306.07882v2 [cond-mat.mes-hall] UPDATED)
Udai Prakash Tyagi, Partha Goswami

The ferromagnetic Weyl semimetals, such as Co3Sn2S2, feature pairs of Weyl points characterized by the opposite chiralities.We model this type of semimetals by the inversion symmetry protected and the time reversal symmetry broken Bloch Hamiltonian. It involves terms representing the tunnelling effect, exchange field corresponding to the ferromagnetic order, chirality index of Weyl points with related energy parameter, and the angle formed by the spin magnetic moments and the axis perpendicular to the system-plane. While the in-plane spin order lacks the presence of the Weyl nodes at some points in the Brillouin zone, the bands of opposite chirality almost linearly cross each other with band inversion at Weyl points above and below the Fermi level for the order along the perpendicular axis. We also show that in the absence of the exchange field, the incidence of the circularly polarized radiation leads to the emergence of a novel state with broken time reversal symmetry.


Fermionic condensate and the vacuum energy-momentum tensor for planar fermions in homogeneous electric and magnetic fields. (arXiv:2306.11402v2 [hep-th] UPDATED)
V. V. Parazian

We consider a massive fermionic quantum field localized on a plane in external constant and homogeneous electric and magnetic fields. The magnetic field is perpendicular to the plane and the electric field is parallel. The complete set of solutions to the Dirac equation is presented. As important physical characteristics of the vacuum state, the fermion condensate and the expectation value of the energy-momentum tensor are investigated. The renormalization is performed using the Hurwitz function. The results are compared with those previously studied in the case of zero electric field. We discuss the behavior of the vacuum expectation values in different regions for the values of the problem parameters. Applications of the results include the electronic subsystem of graphene sheet described by the Dirac model in the long-wavelength approximation.


Strongly disordered Anderson insulator chains with generic two-body interaction. (arXiv:2306.14613v2 [cond-mat.stat-mech] UPDATED)
B. Krajewski, L. Vidmar, J. Bonca, M. Mierzejewski

The random-field spin-1/2 XXZ chains, and the corresponding Anderson insulators of spinless fermions with density-density interaction, have been intensively studied in the context of many-body localization. However, we recently argued [B. Krajewski et al., Phys. Rev. Lett. 129, 260601(2022)] that the two-body density-density interaction in these models is not generic since only a small fraction of this interaction represents a true local perturbation to the Anderson insulator. Here we study ergodicity of strongly disordered Anderson insulator chains choosing other forms of the two-body interaction for which the strength of the true perturbation is of the same order of magnitude as the bare two-body interaction. Focusing on the strong interaction regime, numerical results for the level statistics and the eigenstate thermalization hypothesis are consistent with emergence of ergodicity at arbitrary strong disorder.


Solitonic symmetry as non-invertible symmetry: cohomology theories with TQFT coefficients. (arXiv:2307.00939v2 [hep-th] UPDATED)
Shi Chen, Yuya Tanizaki

Originating from the topology of the path-integral target space $Y$, solitonic symmetry describes the conservation law of topological solitons and the selection rule of defect operators. As Ref.~\cite{Chen:2022cyw} exemplifies, the conventional treatment of solitonic symmetry as an invertible symmetry based on homotopy groups is inappropriate. In this paper, we develop a systematic framework to treat solitonic symmetries as non-invertible generalized symmetries. We propose that the non-invertible solitonic symmetries are generated by the partition functions of auxiliary topological quantum field theories (TQFTs) coupled with the target space $Y$. We then understand solitonic symmetries as non-invertible cohomology theories on $Y$ with TQFT coefficients. This perspective enables us to identify the invertible solitonic subsymmetries and also clarifies the topological origin of the non-invertibility in solitonic symmetry. We finally discuss how solitonic symmetry relies on and goes beyond the conventional wisdom of homotopy groups. This paper is aimed at a tentative general framework for solitonic symmetry, serving as a starting point for future developments.


Direct and Indirect methods of electrocaloric effect determination and energy storage calculation in (Na0.8K0.2)0.5Bi0.5TiO3 ceramic. (arXiv:2307.16232v2 [cond-mat.mtrl-sci] UPDATED)
Pravin Varade, Adityanarayan H. Pandey, N. Shara Sowmya, S. M. Gupta, Abhay Bhisikar, N. Venkataramani, A. R. Kulkarni

The coexistence of multiple structural phases and field induced short-range to long-range order transition in ferroelectric materials, leads to a strong electrocaloric effect (ECE) and electrical energy storage density (Wrec) in the vicinity of ferroelectric to non-ergodic phase transition in NKBT ceramic. Structural analysis using X-ray diffraction, Raman spectroscopy and TEM studies ascertained the coexistence of tetragonal (P4mm) and rhombohedral (R3c) phases. Dielectric study has revealed a critical slowing down of polar domain dynamics below a diffuse phase transition. Present investigation reports ECE in lead-free (Na0.8K0.2)0.5Bi0.5TiO3 (NKBT) ceramic by direct and indirect methods, which confirm the multifunctional nature of NKBT and its usefulness for applications in refrigeration and energy storage. A direct method of EC measurement in NKBT ceramic exhibits significant adiabatic temperature change ({\Delta}T) ~ 1.10 K and electrocaloric strength ({\xi}) ~ 0.55 Kmm/kV near the ferroelectric to non-ergodic phase transition at an external applied field of 20 kV/cm. A highest recoverable energy (Wrec) ~ 0.78 J/cm3 and electrical storage efficiency ({\eta}) ~ 86% are achieved at 423 K and an applied field of 20 kV/cm. This behavior is ascribed to the delicate balance between the field induced order-disordered transition and the thermal energy needed to disrupt field induced co-operative interaction.


Found 7 papers in prb
Date of feed: Tue, 08 Aug 2023 03:17:08 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]+)

Defects in graphene: A topological description
Amit Goft, Yuval Abulafia, Nadav Orion, Claude L. Schochet, and Eric Akkermans
Author(s): Amit Goft, Yuval Abulafia, Nadav Orion, Claude L. Schochet, and Eric Akkermans

Specific types of spatial defects or potentials can turn monolayer graphene into a topological material. These topological defects are classified by a spatial dimension $D$ and they are systematically obtained from the Hamiltonian by means of its symbol $\mathcal{H}(\mathbit{k},\mathbit{r})$, an ope…


[Phys. Rev. B 108, 054101] Published Mon Aug 07, 2023

Allosteric impurity effects in long spin chains
Christian Eidecker-Dunkel and Peter Reimann
Author(s): Christian Eidecker-Dunkel and Peter Reimann

Allosterism traditionally refers to local changes in an extended object, for instance the binding of a ligand to a macromolecule, leading to a localized response at some other, possibly quite remote position. Here, we show that such fascinating effects may already occur in very simple and common qua…


[Phys. Rev. B 108, 054407] Published Mon Aug 07, 2023

Anisotropy of the spin Hall effect in a Dirac ferromagnet
Guanxiong Qu, Masamitsu Hayashi, Masao Ogata, and Junji Fujimoto
Author(s): Guanxiong Qu, Masamitsu Hayashi, Masao Ogata, and Junji Fujimoto

We study the intrinsic spin Hall effect of a Dirac Hamiltonian system with ferromagnetic exchange coupling, a minimal model combining relativistic spin-orbit interaction and ferromagnetism. The energy bands of the Dirac Hamiltonian are split after introducing a Stoner-type ferromagnetic ordering, wh…


[Phys. Rev. B 108, 064404] Published Mon Aug 07, 2023

Intrinsic and tunable quantum anomalous Hall effect and magnetic topological phases in $XY\mathrm{Bi}{}_{2}\mathrm{Te}{}_{5}$
Xin-Yi Tang, Zhe Li, Feng Xue, Pengfei Ji, Zetao Zhang, Xiao Feng, Yong Xu, Quansheng Wu, and Ke He
Author(s): Xin-Yi Tang, Zhe Li, Feng Xue, Pengfei Ji, Zetao Zhang, Xiao Feng, Yong Xu, Quansheng Wu, and Ke He

By first-principles calculations, we study the magnetic and topological properties of $\mathit{XY}{\mathrm{Bi}}_{2}{\mathrm{Te}}_{5}$-family $(X, Y=\mathrm{Mn},\mathrm{Ni},\mathrm{V},\mathrm{Eu})$ compounds. The strongly coupled double magnetic atom-layers can significantly enhance the magnetic orde…


[Phys. Rev. B 108, 075117] Published Mon Aug 07, 2023

Energy-valley-dependent charge transfer in few-layer transition metal dichalcogenide heterostructures
Pavel Valencia-Acuna, Stephanie Amos, Hartwin Peelaers, and Hui Zhao
Author(s): Pavel Valencia-Acuna, Stephanie Amos, Hartwin Peelaers, and Hui Zhao

The effect of the energy valley on interlayer charge transfer in transition metal dichalcogenide (TMD) heterostructures is studied by transient absorption spectroscopy and density functional theory. First-principles calculations confirm that the ${\mathrm{Λ}}_{\text{min}}$ valley in the conduction b…


[Phys. Rev. B 108, 085302] Published Mon Aug 07, 2023

Crystal structure and electrical and optical properties of two-dimensional group-IV monochalcogenides
Mateus B. P. Querne, Jean M. Bracht, Juarez L. F. Da Silva, Anderson Janotti, and Matheus P. Lima
Author(s): Mateus B. P. Querne, Jean M. Bracht, Juarez L. F. Da Silva, Anderson Janotti, and Matheus P. Lima

Two-dimensional (2D) semiconductor materials offer a platform for unconventional applications such as valleytronics, flexible nanoelectronics, and hosts of quantum emitters. Many of these materials and their electronic properties remain to be explored. Using ab initio simulations based on the densit…


[Phys. Rev. B 108, 085409] Published Mon Aug 07, 2023

Half-quantum flux in spin-triplet superconducting rings with bias current
Kazushi Aoyama
Author(s): Kazushi Aoyama

Effects of a bias electric current have been theoretically investigated in a spin-triplet superconducting ring in a magnetic field. Based on the Ginzburg-Landau theory, we show that the bias current can stabilize a half-quantum-flux (HQF) state via couplings to the Zeeman field and the dipole-type s…


[Phys. Rev. B 108, L060502] Published Mon Aug 07, 2023

Found 4 papers in prl
Date of feed: Tue, 08 Aug 2023 03:17:09 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]+)

Self-Healing of Trotter Error in Digital Adiabatic State Preparation
Lucas K. Kovalsky, Fernando A. Calderon-Vargas, Matthew D. Grace, Alicia B. Magann, James B. Larsen, Andrew D. Baczewski, and Mohan Sarovar
Author(s): Lucas K. Kovalsky, Fernando A. Calderon-Vargas, Matthew D. Grace, Alicia B. Magann, James B. Larsen, Andrew D. Baczewski, and Mohan Sarovar

Adiabatic time evolution can be used to prepare a complicated quantum many-body state from one that is easier to synthesize and Trotterization can be used to implement such an evolution digitally. The complex interplay between nonadiabaticity and digitization influences the infidelity of this proces…


[Phys. Rev. Lett. 131, 060602] Published Mon Aug 07, 2023

Raman Scattering Errors in Stimulated-Raman-Induced Logic Gates in $^{133}{\mathrm{Ba}}^{+}$
Matthew J. Boguslawski, Zachary J. Wall, Samuel R. Vizvary, Isam Daniel Moore, Michael Bareian, David T. C. Allcock, David J. Wineland, Eric R. Hudson, and Wesley C. Campbell
Author(s): Matthew J. Boguslawski, Zachary J. Wall, Samuel R. Vizvary, Isam Daniel Moore, Michael Bareian, David T. C. Allcock, David J. Wineland, Eric R. Hudson, and Wesley C. Campbell

$^{133}{\mathrm{Ba}}^{+}$ is illuminated by a laser that is far detuned from optical transitions, and the resulting spontaneous Raman scattering rate is measured. The observed scattering rate is lower than previous theoretical estimates. The majority of the discrepancy is explained by a more accurat…


[Phys. Rev. Lett. 131, 063001] Published Mon Aug 07, 2023

Coherent-Phonon-Driven Intervalley Scattering and Rabi Oscillation in Multivalley 2D Materials
Chenyu Wang, Xinbao Liu, Qing Chen, Daqiang Chen, Yaxian Wang, and Sheng Meng
Author(s): Chenyu Wang, Xinbao Liu, Qing Chen, Daqiang Chen, Yaxian Wang, and Sheng Meng

Resolving the complete electron scattering dynamics mediated by coherent phonons is crucial for understanding electron-phonon couplings beyond equilibrium. Here we present a time-resolved theoretical investigation on strongly coupled ultrafast electron and phonon dynamics in monolayer ${\mathrm{WSe}…


[Phys. Rev. Lett. 131, 066401] Published Mon Aug 07, 2023

Anti-Parity-Time Symmetry in a Su-Schrieffer-Heeger Sonic Lattice
Bolun Hu, Zhiwang Zhang, Zichong Yue, Danwei Liao, Yimin Liu, Haixiao Zhang, Ying Cheng, Xiaojun Liu, and Johan Christensen
Author(s): Bolun Hu, Zhiwang Zhang, Zichong Yue, Danwei Liao, Yimin Liu, Haixiao Zhang, Ying Cheng, Xiaojun Liu, and Johan Christensen

A novel acoustic Su-Schrieffer-Heeger chain with non-Hermitian components displays a non-Hermitian phase transition and reveals new acoustic topological interface states with tunable robust confinement.


[Phys. Rev. Lett. 131, 066601] Published Mon Aug 07, 2023

Found 1 papers in prx
Date of feed: Tue, 08 Aug 2023 03:17:09 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]+)

Observation of First-Order Quantum Phase Transitions and Ferromagnetism in Twisted Double Bilayer Graphene
Le Liu, Xin Lu, Yanbang Chu, Guang Yang, Yalong Yuan, Fanfan Wu, Yiru Ji, Jinpeng Tian, Kenji Watanabe, Takashi Taniguchi, Luojun Du, Dongxia Shi, Jianpeng Liu, Jie Shen, Li Lu, Wei Yang, and Guangyu Zhang
Author(s): Le Liu, Xin Lu, Yanbang Chu, Guang Yang, Yalong Yuan, Fanfan Wu, Yiru Ji, Jinpeng Tian, Kenji Watanabe, Takashi Taniguchi, Luojun Du, Dongxia Shi, Jianpeng Liu, Jie Shen, Li Lu, Wei Yang, and Guangyu Zhang

Experiments on twisted double bilayer graphene reveal the ferromagnetic long-range order and various first-order quantum phase transitions between different broken symmetry states.


[Phys. Rev. X 13, 031015] Published Mon Aug 07, 2023

Found 1 papers in nat-comm


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

Interplay of structure and photophysics of individualized rod-shaped graphene quantum dots with up to 132 sp² carbon atoms
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Found 1 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]+)

Chiral and helical states in selective-area epitaxial heterostructure
Qing Lin He

Communications Physics, Published online: 07 August 2023; doi:10.1038/s42005-023-01328-4

The quantum anomalous Hall effect is a transport phenomenon that has implications in the search for Majorana fermions and quantum metrology. Here, the authors prepare a quantum anomalous Hall bar composed of a magnetic/non-magnetic topological insulating selective-area heterostructure and observe a modulation of the chiral and helical transports at the interface between the two materials by transport measurements.