Found 33 papers in cond-mat
Date of feed: Fri, 17 Nov 2023 01:30:00 GMT

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Kagome Materials II: SG 191: FeGe as a LEGO Building Block for the Entire 1:6:6 series: hidden d-orbital decoupling of flat band sectors, effective models and interaction Hamiltonians. (arXiv:2311.09290v1 [cond-mat.str-el])
Yi Jiang, Haoyu Hu, Dumitru Călugăru, Claudia Felser, Santiago Blanco-Canosa, Hongming Weng, Yuanfeng Xu, B. Andrei Bernevig

The electronic structure and interactions of kagome materials such as 1:1 (FeGe class) and 1:6:6 (MgFe$_6$Ge$_6$ class) are complicated and involve many orbitals and bands at the Fermi level. Current theoretical models treat the systems in an $s$-orbital kagome representation, unsuited and incorrect both quantitatively and qualitatively to the material realities. In this work, we lay the basis of a faithful framework of the electronic model for this large class of materials. We show that the complicated ``spaghetti" of electronic bands near the Fermi level can be decomposed into three groups of $d$-Fe orbitals coupled to specific Ge orbitals. Such decomposition allows for a clear analytical understanding (leading to different results than the simple $s$-orbital kagome models) of the flat bands in the system based on the $S$-matrix formalism of generalized bipartite lattices. Our three minimal Hamiltonians can reproduce the quasi-flat bands, van Hove singularities, topology, and Dirac points close to the Fermi level, which we prove by extensive ab initio studies. We also obtain the interacting Hamiltonian of $d$ orbitals in FeGe using the constraint random phase approximation (cRPA) method. We then use this as a fundamental ``LEGO"-like building block for a large family of 1:6:6 kagome materials, which can be obtained by doubling and perturbing the FeGe Hamiltonian. We applied the model to its kagome siblings FeSn and CoSn, and also MgFe$_6$Ge$_6$. Our work serves as the first complete framework for the study of the interacting phase diagram of kagome compounds.

Topological aspects of brane fields: solitons and higher-form symmetries. (arXiv:2311.09293v1 [hep-th])
Salvatore D. Pace, Yu Leon Liu

In this note, we classify topological solitons of $n$-brane fields, which are nonlocal fields that describe $n$-dimensional extended objects. We consider a class of $n$-brane fields that formally define a homomorphism from the $n$-fold loop space $\Omega^n X_D$ of spacetime $X_D$ to a space $\mathcal{E}_n$. Examples of such $n$-brane fields are Wilson operators in $n$-form gauge theories. The solitons are singularities of the $n$-brane field, and we classify them using the homotopy theory of ${\mathbb{E}_n}$-algebras. We find that the classification of codimension ${k+1}$ topological solitons with ${k\geq n}$ can be understood understood using homotopy groups of $\mathcal{E}_n$. In particular, they are classified by ${\pi_{k-n}(\mathcal{E}_n)}$ when ${n>1}$ and by ${\pi_{k-n}(\mathcal{E}_n)}$ modulo a ${\pi_{1-n}(\mathcal{E}_n)}$ action when ${n=0}$ or ${1}$. However, for ${n>2}$, their classification goes beyond the homotopy groups of $\mathcal{E}_n$ when ${k< n}$, which we explore through examples. We compare this classification to $n$-form $\mathcal{E}_n$ gauge theory. We then apply this classification and consider an ${n}$-form symmetry described by the abelian group ${G^{(n)}}$ that is spontaneously broken to ${H^{(n)}\subset G^{(n)}}$, for which the order parameter characterizing this symmetry breaking pattern is an ${n}$-brane field with target space ${\mathcal{E}_n = G^{(n)}/H^{(n)}}$. We discuss this classification in the context of many examples, both with and without 't Hooft anomalies.

First-order effect of electron-electron interactions on the anomalous Hall conductivity of massive Dirac fermions. (arXiv:2311.09304v1 [cond-mat.mes-hall])
Daria A. Dumitriu-I., Darius A. Deaconu, Alexander E. Kazantsev, Alessandro Principi

We investigate the first-order correction to the anomalous Hall conductivity of 2D massive Dirac fermions arising from electron-electron interactions. In a fully gapped system in the limit of zero temperature, we find that this correction vanishes, confirming the absence of perturbative corrections to the topological Hall conductivity. At finite temperature or chemical potential, we find that the total Hall response decays faster than in the non-interacting case, depending on the strength of electron-electron interactions. These features, which could potentially be observed experimentally, show the importance of two-body interactions for anomalous Hall transport.

Lattice Hamiltonian for Adjoint QCD$_2$. (arXiv:2311.09334v1 [hep-th])
Ross Dempsey, Igor R. Klebanov, Silviu S. Pufu, Benjamin T. Søgaard

We introduce a Hamiltonian lattice model for the $(1+1)$-dimensional $\text{SU}(N_c)$ gauge theory coupled to one adjoint Majorana fermion of mass $m$. The discretization of the continuum theory uses staggered Majorana fermions. We analyze the symmetries of the lattice model and find lattice analogs of the anomalies of the corresponding continuum theory. An important role is played by the lattice translation by one lattice site, which in the continuum limit involves a discrete axial transformation. On a lattice with periodic boundary conditions, the Hilbert space breaks up into sectors labeled by the $N_c$-ality $p=0, \ldots N_c-1$. Our symmetry analysis implies various exact degeneracies in the spectrum of the lattice model. In particular, it shows that, for $m=0$ and even $N_c$, the sectors $p$ and $p'$ are degenerate if $|p-p'| = N_c/2$. In the $N_c = 2$ case, we explicitly construct the action of the Hamiltonian on a basis of gauge-invariant states, and we perform both a strong coupling expansion and exact diagonalization for lattices of up to $12$ lattice sites. Upon extrapolation of these results, we find good agreement with the spectrum computed previously using discretized light-cone quantization. One of our new results is the first numerical calculation of the fermion bilinear condensate.

Possible Topological Superconductivity in a Topological Crystalline Insulator (Pb$_{1-x}$Sn$_x$)$_{1-y}$In$_y$Te. (arXiv:2311.09368v1 [cond-mat.supr-con])
I. Pletikosic, T. Yilmaz, B. Sinkovic, A. P. Weber, G. D. Gu, T. Valla

Superconductivity in topological insulators is expected to show very unconventional features such as $p+ip$ order parameter, Majorana fermions etc. However, the intrinsic superconductivity has been observed in a very limited number of materials in which the pairing symmetry is still a matter of debate. Here, we study the topological crystalline insulator (Pb$_{1-x}$Sn$_x$)$_{1-y}$In$_y$Te, where a peculiar insulator to superconductor transition was previously reported near the gap inversion transition, when the system is nearly a 3-dimensional Dirac semimetal. Both the existence of superconductivity near the 3-dimensional Dirac semimetal and the occurrence of insulator to superconductor transition in an isotropic material is highly unusual. We suggest that the observed phenomena are related to an intrinsic instability of a 3-dimensional Dirac semimetal state in (Pb$_{1-x}$Sn$_x$)$_{1-y}$In$_y$Te and "flattening" of the bulk valence and conduction bands as they acquire a Mexican hat-like dispersion on the inverted side of the phase diagram. This favors the pairing instability if the chemical potential is pinned to these flat regions.

Flat Bands at the Fermi Level in Unconventional Superconductor YFe2Ge2. (arXiv:2311.09492v1 [cond-mat.str-el])
R. Kurleto, C.-H. Wu, S. Acharya, D.M. Narayan, B.S. Berggren, P. Hao, A. Shackelford, H.R. Whitelock, Z. Sierzega, M. Hashimoto, D. Lu, C. Jozwiak, R.P. Cline, D. Pashov, J. Chen, M. van Schilfgaarde, F.M. Grosche, D.S. Dessau

We report heavy electron behavior in unconventional superconductor YFe$_2$Ge$_2$ ($T_C \,{=}\, 1.2$ K). We directly observe very heavy bands ($m_\mathrm{eff}\sim 25 m_e$) within $\sim$10 meV of the Fermi level $E_{F}$ using angle-resolved photoelectron spectroscopy (ARPES). The flat bands reside at the X points of the Brillouin zone and are composed principally of $d_{xz}$ and $d_{yz}$ orbitals. We utilize many-body perturbative theory, GW, to calculate the electronic structure of this material, obtaining excellent agreement with the ARPES data with relatively minor band renormalizations and band shifting required. We obtain further agreement at the Dynamical Mean Field Theory (DMFT) level, highlighting the emergence of the many-body physics at low energies (near $E_F$) and temperatures.

Revealing inverted chirality of hidden domain wall states in multiband systems without topological transition. (arXiv:2311.09493v1 [cond-mat.mes-hall])
Seung-Gyo Jeong, Sang-Hoon Han, Tae-Hwan Kim, Sangmo Cheon

Chirality, a fundamental concept from biological molecules to advanced materials, is prevalent in nature. Yet, its intricate behavior in specific topological systems remains poorly understood. Here, we investigate the emergence of hidden chiral domain wall states using a double-chain Su-Schrieffer-Heeger model with interchain coupling specifically designed to break chiral symmetry. Our phase diagram reveals single-gap and double-gap phases based on electronic structure, where transitions occur without topological phase changes. In the single-gap phase, we reproduce chiral domain wall states, akin to chiral solitons in the double-chain model, where chirality is encoded in the spectrum and topological charge pumping. In the double-gap phase, we identify hidden chiral domain wall states exhibiting opposite chirality to the domain wall states in the single-gap phase, where the opposite chirality is confirmed through spectrum inversion and charge pumping as the corresponding domain wall slowly moves. By engineering gap structures, we demonstrate control over hidden chiral domain states. Our findings open avenues to investigate novel topological systems with broken chiral symmetry and potential applications in diverse systems.

Dissipation Enhanced Unidirectional Transport in Topological Systems. (arXiv:2311.09534v1 [cond-mat.mes-hall])
Ming Lu, Xue-Zhu Liu, Hailong Li, Zhi-Qiang Zhang, Jie Liu, X.C. Xie

Dissipation is a common occurrence in real-world systems and is generally considered to be detrimental to transport. In this study, we examine the transport properties of a narrow quantum anomalous Hall system with dissipation applied on one edge. When the Fermi level resides within the hybridization gap, we find that while transport is suppressed on one edge, it is significantly enhanced on the other. We reveal that this enhancement arises from dissipation-induced gap closure, which is deeply rooted in the point gap topology of the system, resulting in a reduction of the decaying coefficient. When the dissipation is very large, we find that the low-energy physics is nearly indistinguishable from a narrower system, whose dissipation amplitude is inversely proportional to that of the original one. To get more physical intuition, we demonstrate that the low-energy physics can be well captured by a pair of coupled counter-propagating chiral edge states, one of which has a modified group velocity and an effective dissipation. We also briefly discuss the possible experimental realizations of this enhanced unidirectional transport.

Light-induced ideal Weyl semimetal in HgTe via nonlinear phononics. (arXiv:2311.09583v1 [cond-mat.mtrl-sci])
Dongbin Shin, Angel Rubio, Peizhe Tang

Interactions between light and matter allow the realization of out-of-equilibrium states in quantum solids. In particular, nonlinear phononics is one of the efficient approaches to realizing the stationary electronic state in non-equilibrium. Herein, by using extended $ab~initio$ molecular dynamics, we identify that long-lived light-driven quasi-stationary geometry could stabilize the topological nature in the material family of HgTe compounds. We show that coherent excitation of the infrared-active phonon mode results in a distortion of the atomic geometry with a lifetime of several picoseconds. We show that four Weyl points are located exactly at the Fermi level in this non-equilibrium geometry, making it an ideal long-lived metastable Weyl semimetal. We propose that such a metastable topological phase can be identified by photoelectron spectroscopy of the Fermi arc surface states or ultrafast pump-probe transport measurements of the nonlinear Hall effect.

Weak breakdown of bulk-boundary correspondence in a symmetry-protected topological phase out-of-equilibrium. (arXiv:2311.09610v1 [cond-mat.str-el])
Thomas L. M. Lane, Miklós Horváth, Kristian Patrick

Time evolution of topological systems is an active area of interest due to their expected uses in fault tolerant quantum computing. Here, we analyze the dynamics of a non-interacting spinless fermion chain in its topological phase, when the system is quenched out-of-equilibrium by a Hamiltonian belonging to the same symmetry class. Due to the presence of particle-hole symmetry, we find that the bulk properties of the system remain intact throughout the evolution. However, the boundary properties may be drastically altered, where we see delocalization of initially localized Majorana edge modes. The presence of local static disorder can be utilized to preserve exponential localization, yet we still identify non-trivial dynamics in the Majorana polarization and Loschmidt echo. We find that, due to delocalization, the entanglement spectrum is no longer a good indicator of the bulk topological phase, as the system remains non-trivial while degeneracies in the many-body entanglement spectrum are lost.

Quantum-anomalous-Hall current patterns and interference in thin slabs of chiral topological superconductors. (arXiv:2311.09664v1 [cond-mat.mes-hall])
Daniele Di Miceli, Llorenç Serra

The chiral topological superconductor, which supports propagating nontrivial edge modes while maintaining a gapped bulk, can be realized hybridizing a quantum-anomalous-Hall thin slab with an ordinary $s$-wave superconductor. We show that by sweeping the voltage bias in a normal-hybrid-normal double junction, the pattern of electric currents in the normal leads spans three main regimes. From single-mode edge-current quantization at low bias, to double-mode edge-current oscillations at intermediate voltages and up to diffusive bulk currents at larger voltages. Observing such patterns by resolving the spatial distribution of the local current in the thin slab could provide additional evidence, besides the global conductance, on the physics of chiral topological superconductors.

Comprehensive Quantum Calculation of the First Dielectric Virial Coefficient of Water. (arXiv:2311.09722v1 [physics.chem-ph])
Giovanni Garberoglio, Chiara Lissoni, Luca Spagnoli, Allan H. Harvey

We present a complete calculation, fully accounting for quantum effects and for molecular flexibility, of the first dielectric virial coefficient of water and its isotopologues. The contribution of the electronic polarizability is computed from a state-of-the-art intramolecular potential and polarizability surface from the literature, and its small temperature dependence is quantified. The dipolar polarizability is calculated in a similar manner with an accurate literature dipole-moment surface; it differs from the classical result both due to the different molecular geometries sampled at different temperatures and due to the quantization of rotation. We calculate the dipolar contribution independently from spectroscopic information in the HITRAN2020 database and find that the two methods yield consistent results. The resulting first dielectric virial coefficient provides a complete description of the dielectric constant at low density that can be used in humidity metrology and as a boundary condition for new formulations for the static dielectric constant of water and heavy water.

Observation of zero-energy modes in Gd atomic chains on superconducting Nb(110). (arXiv:2311.09742v1 [cond-mat.supr-con])
Yu Wang, Felix Friedrich, Matthias Bode, Artem Odobesko

In this experimental study, we use scanning tunneling microscopy and spectroscopy to investigate Yu-Shiba-Rusinov states induced by 4f-shell rare-earth Gd adatoms on a superconducting Nb(110) surface. We engineer Gd atom chains along the substrate's $[1\overline{1}0]$ and $[001]$ directions, revealing distinct behaviors in differently oriented chains. $[1\overline{1}0]$-oriented Gd chains exhibit spectroscopic features at their ends, identifying them as trivial edge states, while $[001]$-oriented Gd chains display zero-energy edge states, suggesting non-trivial nature. Notably, Gd chains with four atoms--independent of their particular orientation--exhibit a uniform zero-energy mode along the entire chain. These findings call for further research and a theoretical framework to describe rare-earth-based structures on superconductors.

Spin-phonon interactions on the kagome lattice: Dirac spin liquid versus valence-bond solids. (arXiv:2311.09823v1 [cond-mat.str-el])
Francesco Ferrari, Federico Becca, Roser Valenti

We investigate the impact of the spin-phonon coupling on the S=1/2 Heisenberg model on the kagome lattice. For the pure spin model, there is increasing evidence that the low-energy properties can be correctly described by a Dirac spin liquid, in which spinons with a conical dispersion are coupled to emergent gauge fields. Within this scenario, the ground-state wave function is well approximated by a Gutzwiller-projected fermionic state [Y. Ran, M. Hermele, P.A. Lee, and X.-G. Wen, Phys. Rev. Lett. 98, 117205 (2007)]. However, the existence of U(1) gauge fields may naturally lead to instabilities when small perturbations are included. Since phonons are ubiquitous in real materials, they may play a relevant role in the determination of the actual physical properties of the kagome antiferromagnet. We perform a step forward in this direction, including phonon degrees of freedom (at the quantum level) and applying a variational approach based upon Gutzwiller-projected fermionic Ans\"atze. Our results suggest that the Dirac spin liquid is stable for small spin-phonon couplings, while valence-bond solids are obtained at large couplings. Even though different distortions can be induced by the spin-phonon interaction, the general aspect is that the energy is lowered by maximizing the density of perfect hexagons in the dimerization pattern.

Scoring Anomalous Vertices Through Quantum Walks. (arXiv:2311.09855v1 [quant-ph])
Andrew Vlasic, Anh Pham

With the explosion of data over the past decades there has been a respective explosion of techniques to extract information from the data from labeled data, quasi-labeled data, and data with no labels known a priori. For data with at best quasi-labels, graphs are a natural structure to connect points to further extract information. In particular, anomaly detection in graphs is a method to determine which data points do not posses the latent characteristics of the other data. There have been a variety of classical methods to score vertices on their anomalous level with respect to the graph, spanning straightforward methods of checking the local topology of a node to intricate neural networks. Leveraging the structure of the graph, we propose a first ever quantum-based technique to calculate the anomaly score of each node by continuously traversing the graph in a particular manner. The proposed algorithm incorporates well-known characteristics of quantum random walks, and an adjustment to the algorithm is given to mitigate the increasing depth of the circuit. This algorithm is rigorously shown to converge to the expected probability, with respect to the initial condition.

Study on the effects of anisotropic effective mass on electronic properties, magnetization and persistent current in semiconductor quantum ring with conical geometry. (arXiv:2311.09859v1 [cond-mat.mes-hall])
Francisco A. G. de Lira, Luís Fernando C. Pereira, Edilberto O. Silva

We study a 2D mesoscopic ring with an anisotropic effective mass considering surface quantum confinement effects. Consider that the ring is defined on the surface of a cone, which can be controlled topologically and mapped to the 2D ring in flat space. We demonstrate through numerical analysis that the electronic properties, the magnetization, and the persistent current undergo significant changes due to quantum confinement and non-isotropic mass. We investigate these changes in the direct band gap semiconductors SiC, ZnO, GaN, and AlN. There is a plus (or minus) shift in the energy sub-bands for different values of curvature parameter and anisotropy. Manifestations of this nature are also seen in the Fermi energy profile as a function of the magnetic field and in the ring width as a function of the curvature parameter. Aharonov-Bohm (AB) and de Haas van-Alphen (dHvA) oscillations are also studied, and we find that they are sensitive to variations in curvature and anisotropy.

Rashba spin splitting and Dirac fermions in monolayer PtSe$_2$ nanoribbons. (arXiv:2311.09931v1 [cond-mat.mes-hall])
Bo-Wen Yu, Bang-Gui Liu

Two-dimensional (2D) semiconducting transition metal dichalcogenides have potential applications in various fields. Recently, it is shown experimentally and theoretically that monolayer PtSe$_2$ nanoflakes with neutral edges are stable. Here, we study PtSe$_2$ nanoribbons with the stable zigzag edges through first-principles investigation and find Rashba spin splitting and gapped relativstic electron dispersion in their valence and conduction bands near the Fermi level. Our analysis of atom-projected band structures and densities of states indicates that the part of bands originates mainly from the edges of the nanoribbons. It is also shown that there exists a SU(2) spin symmetry in both valence and conduction band edges, which implies persistent spin helix along the edges. Furthermore, we can achieve a Dirac electron model for an edge by combining the valence and conduction bands when the inter-edge interaction is week. These electronic systems could be useful for designing high-performance spintronic and optoelectronic applications.

Non-Hermitian topology and criticality in photonic arrays with engineered losses. (arXiv:2311.09959v1 [physics.optics])
Elizabeth Louis Pereira, Hongwei Li, Andrea Blanco-Redondo, Jose L. Lado

Integrated photonic systems provide a flexible platform where artificial lattices can be engineered in a reconfigurable fashion. Here, we show that one-dimensional photonic arrays with engineered losses allow realizing topological excitation stemming from non-Hermiticity and bulk mode criticality. We show that a generalized modulation of the local photonic losses allow creating topological modes both in the presence of periodicity and even in the quasiperiodic regime. We demonstrate that a localization transition of all the bulk photonic modes can be engineered in the presence of a quasiperiodic loss modulation, and we further demonstrate that such a transition can be created in the presence of both resonance frequency modulation and loss modulation. We finally address the robustness of this phenomenology to the presence of higher neighbor couplings and disorder in the emergence of criticality and topological modes. Our results put forward a strategy to engineer topology and criticality solely from engineered losses in a photonic system, establishing a potential platform to study the impact of non-linearities in topological and critical photonic matter.

Fermi surface symmetric mass generation: a quantum Monte-Carlo study. (arXiv:2311.09970v1 [cond-mat.str-el])
Wei-Xuan Chang, Sibo Guo, Yi-Zhuang You, Zi-Xiang Li

The symmetric mass generation (SMG) phase is an insulator in which a single-particle gap is intrinsically opened by the interaction, without involving symmetry spontaneously breaking or topological order. Here, we perform unbiased quantum Monte-Carlo simulation and systematically investigate a bilayer fermionic model hosting Fermi surface SMG in the strongly interacting regime. With increasing interaction strength, the model undergoes a quantum phase transition from an exciton insulator to an SMG phase, belonging to the (2+1)-dimensional O(4) universality class. We access the spectral properties of the SMG phase, resembling a Mott insulating phase with relatively flat dispersion and pronounced spectral broadening. The dispersion of Green's function zeros is extracted from spectral function, featuring a surface at zero frequency precisely located at the original non-interacting Fermi surface, which constitutes a hallmark of the Fermi surface SMG phase. The bilayer model we study is potentially relevant to the newly discovered high-$T_c$ superconductor $\rm{La}_3 \rm{Ni}_2 \rm{O}_7$. Our results in SMG phase qualitatively capture the salient features of spectral function unveiled in recent ARPES experiments, shedding new insight on the underlying physics of $\rm{La}_3 \rm{Ni}_2 \rm{O}_7$.

Dynamic Clustering of Active Rings. (arXiv:2311.10007v1 [cond-mat.soft])
Ligesh Theeyancheri, Subhasish Chaki, Tapomoy Bhattacharjee, Rajarshi Chakrabarti

A collection of rings made of active Brownian particles (ABPs) for different packing fractions and activities is investigated using computer simulations. We show that active rings display an emergent dynamic clustering instead of the conventional motility-induced phase separation (MIPS) as in the case of collection of ABPs. Surprisingly, increasing packing fraction of rings exhibits a non-monotonicity in the dynamics due to the formation of a large number of small clusters. The conformational fluctuations of the polymers suppress the usual MIPS exhibited by ABPs. Our findings demonstrate how the motion of a collection of rings is influenced by the interplay of activity, topology, and connectivity.

Topological Gap Opening without Symmetry Breaking from Dynamical Quantum Correlations. (arXiv:2311.10024v1 [cond-mat.str-el])
Francesca Paoletti, Laura Fanfarillo, Massimo Capone, Adriano Amaricci

Topological phase transitions are typically associated with the formation of gapless states. Spontaneous symmetry breaking can lead to a gap opening thereby obliterating the topological nature of the system. Here we highlight a completely different destiny for a topological transition in presence of interaction. Solving a Bernevig-Hughes-Zhang model with local interaction, we show that dynamical quantum fluctuations can lead to the opening of a gap without any symmetry breaking. As we vary the interaction and the bare mass of the model, the continuous gapless topological transition turns into a first-order one, associated with the presence of massive Dirac fermion at the transition point showing a Gross-Neveu critical behaviour near the quantum critical endpoint. We identify the gap opening as a condensed matter analog of the Coleman-Weinberg mechanism of mass generation.

On valley asymmetry in a topological interaction for quasi-particles. (arXiv:2311.10073v1 [hep-th])
G. B. de Gracia, B. M. Pimentel, R. da Rocha

This paper is focused on investigating the effects of a statistical interaction for graphene-like systems, providing Haldane-like properties for topologically trivial lattices. The associated self-energy correction yields an effective next-nearest hopping, inducing the topological phase, whose specific solutions are scrutinized. In the case of an external magnetic field, it leads to a renormalized quasi-particle structure with generalized Landau levels and explicit valley asymmetry. A suitable tool for implementing such achievements is a judicious indefinite metric quantization, leading to advances in field theory foundations. Since the topological behavior is encoded in the radiative corrections, an unequivocal treatment using an integral representation is carefully developed.

Wave packet dynamics and edge transport in anomalous Floquet topological phases. (arXiv:2302.08485v2 [cond-mat.quant-gas] UPDATED)
Miguel F. Martínez, F. Nur Ünal

The possibility of attaining chiral edge modes under periodic driving has spurred tremendous attention, both theoretically and experimentally, especially in light of anomalous Floquet topological phases that feature vanishing Chern numbers unlike any static counterpart. We here consider a periodically modulated honeycomb lattice and experimentally relevant driving protocols, which allows us to obtain edge modes of various character in a simple model. We calculate the phase diagram over a wide range of parameters and recover an anomalous topological phase with quasienergy gaps harbouring edge states with opposite chirality. Motivated by the advances in single-site control in optical lattices, we investigate wave packet dynamics localized at the edges in distinct Floquet topological regimes that cannot be achieved in equilibrium. We analyse transport properties in edge modes originating from the same bands, but with support at different quasienergies and sublattices as well as possessing different chiralities. We find that an anomalous Floquet topological phase can in general generate more robust chiral edge motion than a Haldane phase. Our results demonstrate that the rich interplay of wave packet dynamics and topological edge states can serve as a versatile tool in ultracold quantum gases in optical lattices.

Time-Reversal Soliton Pairs In Even Spin-Chern-Number Higher-Order Topological Insulators. (arXiv:2303.04031v2 [cond-mat.mes-hall] UPDATED)
Yi-Chun Hung, Baokai Wang, Chen-Hsuan Hsu, Arun Bansil, Hsin Lin

Solitons formed through the one-dimensional mass-kink mechanism on the edges of two-dimensional systems with non-trivial topology play an important role in the emergence of higher-order (HO) topological phases. In this connection, the existing work in time-reversal symmetric systems has focused on gapping the edge Dirac cones in the presence of particle-hole symmetry, which is not suited to the common spin-Chern insulators. Here, we address the emergence of edge solitons in spin-Chern number of $2$ insulators, in which the edge Dirac cones are gapped by perturbations preserving time-reversal symmetry but breaking spin-$U(1)$ symmetry. Through the mass-kink mechanism, we thus explain the appearance of pairwise corner modes and predict the emergence of extra charges around the corners. By tracing the evolution of the mass term along the edge, we demonstrate that the in-gap corner modes and the associated extra charges can be generated through the $S_z$-mixing spin-orbit coupling via the mass-kink mechanism. We thus provide strong evidence that an even spin-Chern-number insulator is an HO topological insulator with protected corner charges.

Breakdown of Conventional Winding Number Calculation in One-Dimensional Lattices with Interactions Beyond Nearest Neighbors. (arXiv:2304.04080v3 [cond-mat.mtrl-sci] UPDATED)
Amir Rajabpoor Alisepahi, Siddhartha Sarkar, Kai Sun, Jihong Ma

Topological insulators hold promises to realize exotic quantum phenomena in electronic, photonic, and phononic systems. Conventionally, topological indices, such as winding numbers, have been used to predict the number of topologically protected domain-wall states (TPDWSs) in topological insulators, a signature of the topological phenomenon called bulk-edge correspondence. Here, we demonstrate theoretically and experimentally that the number of TPDWSs in a mechanical Su-Schrieffer-Heeger (SSH) model can be higher than the winding number depending on the strengths of beyond-nearest-neighbor interactions, revealing the breakdown of the winding number prediction. Alternatively, we resort to the Berry connection to accurately characterize the number and spatial features of TPDWSs in SSH systems, further confirmed by the Jackiw-Rebbi theory proving that the multiple TPDWSs correspond to the bulk Dirac cones. Our findings deepen the understanding of complex network dynamics and offer a generalized paradigm for precise TPDWS prediction in potential applications involving localized vibrations, such as drug delivery and quantum computing.

Information Trapping by Topologically Protected Edge States: Scrambling and the Butterfly Velocity. (arXiv:2306.00527v2 [cond-mat.mes-hall] UPDATED)
Martyna Sedlmayr, Hadi Cheraghi, Nicholas Sedlmayr

Topological insulators and superconductors have attracted considerable attention, and many different theoretical tools have been used to gain insight into their properties. Here we investigate how perturbations can spread through exemplary one-dimensional topological insulators and superconductors using out-of-time ordered correlators. Out-of-time ordered correlators are often used to consider how information becomes scrambled during quantum dynamics. The wavefront of the out-of-time ordered correlator can be ballistic regardless of the underlying system dynamics, and here we confirm that for topological free fermion systems the wavefront spreads linearly at a characteristic butterfly velocity. We pay special attention to the topologically protected edge states, finding that "information" can become trapped in the edge states and essentially decoupled from the bulk, surviving for relatively long times. We consider different models with multiple possible edge states coexisting on a single edge.

Andreev and normal reflections in gapped bilayer graphene-superconductor junctions. (arXiv:2306.00529v2 [cond-mat.supr-con] UPDATED)
Panch Ram, Detlef Beckmann, Romain Danneau, Wolfgang Belzig

We study the Andreev and normal reflection processes -- retro as well as specular -- in a bilayer graphene-superconductor junction where equal and opposite displacement fields are applied for the top and bottom layers to induce a band gap. By employing the Dirac-Bogoliubov-de Gennes equation for the gapped bilayer graphene-superconductor junction, we calculate the reflections probabilities within the scattering theory approach. The subgap conductance, calculated in the framework of Blonder-Tinkham-Klapwijk formalism, shows the contribution from the Andreev retro-reflection (specular-reflection) when the applied bias voltage is below (above) the Fermi energy. Notably, both retro and specular reflections are modified in the presence of the displacement field, and the retro-to-specular crossover gets amplified when the displacement field is relatively small. They can be further tuned to either specular or retro Andreev reflection by adjusting the Fermi energy. Furthermore, our study reveals the simultaneous existence of double Andreev reflections and double normal reflections when the displacement field becomes comparable to the interlayer coupling strength. The existence of the normal retro-reflection process in a bilayer graphene-superconductor junction is a new finding which shows a distinctive feature in the conductance that can be experimentally verified.

Parity-conserving Cooper-pair transport and ideal superconducting diode in planar Germanium. (arXiv:2306.07109v2 [cond-mat.mes-hall] UPDATED)
Marco Valentini, Oliver Sagi, Levon Baghumyan, Thijs de Gijsel, Jason Jung, Stefano Calcaterra, Andrea Ballabio, Juan Aguilera Servin, Kushagra Aggarwal, Marian Janik, Thomas Adletzberger, Rubén Seoane Souto, Martin Leijnse, Jeroen Danon, Constantin Schrade, Erik Bakkers, Daniel Chrastina, Giovanni Isella, Georgios Katsaros

Superconductor/semiconductor hybrid devices have attracted increasing interest in the past years. Superconducting electronics aims to complement semiconductor technology, while hybrid architectures are at the forefront of new ideas such as topological superconductivity and protected qubits. In this work, we engineer the induced superconductivity in two-dimensional germanium hole gas by varying the distance between the quantum well and the aluminum. We demonstrate a hard superconducting gap and realize an electrically and flux tunable superconducting diode using a superconducting quantum interference device (SQUID). This allows to tune the current phase relation (CPR), to a regime where single Cooper pair tunneling is suppressed, creating a $\sin \left( 2 \varphi \right)$ CPR. Shapiro experiments complement this interpretation and the microwave drive allows to create a diode with 100% efficiency. The reported results open up the path towards integration of spin qubit devices, microwave resonators and (protected) superconducting qubits on a silicon technology compatible platform.

Topological Mott insulator in the odd-integer filled Anderson lattice model with Hatsugai-Kohmoto interactions. (arXiv:2308.02292v2 [cond-mat.str-el] UPDATED)
Krystian Jabłonowski, Jan Skolimowski, Wojciech Brzezicki, Krzysztof Byczuk, Marcin M. Wysokiński

Recently, a quantum anomalous Hall state at odd integer filling in moir\'e stacked MoTe$_2$/WSe$_2$ was convincingly interpreted as a topological Mott insulator state appearing due to strong interactions in {\it band} basis [P. Mai, J. Zhao, B. E. Feldman, and P. W. Phillips, Nat. Commun. {\bf 14}, 5999 (2023)]. In this work, we aim to analyze the formation of a topological Mott insulator due to interactions in {\it orbital} basis instead, being more natural for systems where interactions originate from the character of $f$ or $d$ orbitals rather than band flatness. For that reason, we study an odd-integer filled Anderson lattice model incorporating odd-parity hybridization between orbitals with different degrees of correlations introduced in the Hatsugai-Kohmoto spirit. We demonstrate that a topological Mott insulating state can be realized in a considered model only when weak intra- and inter-orbital correlations involving dispersive states are taken into account. Interestingly, we find that all topological transitions between trivial and topological Mott insulating phases are not accompanied by a spectral gap closing, consistent with a phenomenon called {\it first-order topological transition}. Instead, they are signaled by a kink developed in spectral function at one of the time reversal invariant momenta. We believe that our approach can provide insightful phenomenology of topological Mott insulators in spin-orbit coupled $f$ or $d$ electron systems.

The algorithmic second law of thermodynamics. (arXiv:2308.06927v3 [cond-mat.stat-mech] UPDATED)
Aram Ebtekar

G\'acs' coarse-grained algorithmic entropy leverages universal computation to quantify the information content of any given physical state. Unlike the Boltzmann and Shannon-Gibbs entropies, it requires no prior commitment to macrovariables or probabilistic ensembles, rendering it applicable to settings arbitrarily far from equilibrium. For Markovian coarse-grainings, we prove a number of algorithmic fluctuation inequalities. The most important of these is a very general formulation of the second law of thermodynamics. In the presence of a heat and work reservoir, it implies algorithmic versions of Jarzynski's equality and Landauer's principle. Finally, to demonstrate how a deficiency of algorithmic entropy can be used as a resource, we model an information engine powered by compressible strings.

Kekul\'e spirals and charge transfer cascades in twisted symmetric trilayer graphene. (arXiv:2310.16094v2 [cond-mat.str-el] UPDATED)
Ziwei Wang, Yves H. Kwan, Glenn Wagner, Nick Bultinck, Steven H. Simon, S.A. Parameswaran

We study the phase diagram of magic-angle twisted symmetric trilayer graphene in the presence of uniaxial heterostrain and interlayer displacement field. For experimentally reasonable strain, our mean-field analysis finds robust Kekul\'e spiral order whose doping-dependent ordering vector is incommensurate with the moir\'e superlattice, consistent with recent scanning tunneling microscopy experiments, and paralleling the behaviour of closely-related twisted bilayer graphene (TBG) systems. Strikingly, we identify a new possibility absent in TBG: the existence of $\textit{commensurate}$ Kekul\'e spiral order even at zero strain for experimentally realistic values of the interlayer potential in a trilayer. Our studies also reveal a complex pattern of charge transfer between weakly- and strongly-dispersive bands in strained trilayer samples as the density is tuned by electrostatic gating, that can be understood intuitively in terms of the `cascades' in the compressibility of magic-angle TBG.

Translation-invariant relativistic Langevin equation derived from first principles. (arXiv:2310.18327v2 [cond-mat.stat-mech] UPDATED)
Filippo Emanuele Zadra, Aleksandr Petrosyan, Alessio Zaccone

The relativistic Langevin equation poses a number of technical and conceptual problems related to its derivation and underlying physical assumptions. Recently, a method has been proposed in [A. Petrosyan and A. Zaccone, J. Phys. A: Math. Theor. 55 015001 (2022)] to derive the relativistic Langevin equation from a first-principles particle-bath Lagrangian. As a result of the particle-bath coupling, a new ``restoring force'' term appeared, which breaks translation symmetry. Here we revisit this problem aiming at deriving a fully translation-invariant relativistic Langevin equation. We successfully do this by adopting the renormalization potential protocol originally suggested by Caldeira and Leggett. The relativistic renormalization potential is derived here and shown to reduce to Caldeira and Leggett's form in the non-relativistic limit. The introduction of this renormalization potential successfully removes the restoring force and a fully translation-invariant relativistic Langevin equation is derived for the first time. The physically necessary character of the renormalization potential is discussed in analogy with non-relativistic systems, where it emerges due to the renormalization of the tagged particle dynamics due to its interaction with the bath oscillators (a phenomenon akin to level-repulsion or avoided-crossing in condensed matter). We discuss the properties that the corresponding non-Markovian friction kernel has to satisfy, with implications ranging from transport models of the quark-gluon plasma, to relativistic viscous hydrodynamic simulations, and to electrons in graphene.

Lattice relaxation, electronic structure and continuum model for twisted bilayer MoTe$_2$. (arXiv:2311.07533v2 [cond-mat.str-el] UPDATED)
Ning Mao, Cheng Xu, Jiangxu Li, Ting Bao, Peitao Liu, Yong Xu, Claudia Felser, Liang Fu, Yang Zhang

We investigate the lattice relaxation effect on moir\'e band structures in twisted bilayer MoTe$_2$ with two approaches: (a) large-scale plane-wave basis first principle calculation down to $2.88^{\circ}$, (b) transfer learning structure relaxation + local-basis first principles calculation down to $1.1^{\circ}$. Two types of van der Waals corrections have been examined: the D2 method of Grimme and the density-dependent energy correction. We note the density-dependent energy correction yields a continuous evolution of bandwidth with twist angles. Including second harmonic of intralayer potential/interlayer tunneling and the strain induced gauge field, we develop a more complete continuum model with a single set of parameters for a wide range of twist angles, providing a useful starting point for many body simulation.

Found 4 papers in prb
Date of feed: Fri, 17 Nov 2023 04:17:13 GMT

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

Proximate Dirac spin liquid in the honeycomb lattice ${J}_{1}\text{−}{J}_{3}$ XXZ model: Numerical study and application to cobaltates
Anjishnu Bose, Manodip Routh, Sreekar Voleti, Sudip Kumar Saha, Manoranjan Kumar, Tanusri Saha-Dasgupta, and Arun Paramekanti
Author(s): Anjishnu Bose, Manodip Routh, Sreekar Voleti, Sudip Kumar Saha, Manoranjan Kumar, Tanusri Saha-Dasgupta, and Arun Paramekanti

Recent theoretical and experimental work suggests that the honeycomb cobaltates, initially proposed as candidate Kitaev quantum magnets, are in fact described by a pseudospin-$1/2$ easy-plane spin Hamiltonian with nearest-neighbor ferromagnetic (FM) exchange ${J}_{1}$ being frustrated by antiferroma…

[Phys. Rev. B 108, 174422] Published Thu Nov 16, 2023

Physical properties of monolayer $\mathrm{Mn}{(\mathrm{BiTeS})}_{2}$ and its applications in sub–3 nm spintronic devices
Zhanhai Li, Jianing Han, Shengguo Cao, Zhenhua Zhang, and Xiaoqing Deng
Author(s): Zhanhai Li, Jianing Han, Shengguo Cao, Zhenhua Zhang, and Xiaoqing Deng

Half semiconductors, capable of achieving 100% spin-polarized carriers under simple electrostatic gating, optical excitation, and thermal excitation conditions, have emerged as some of the most promising materials for spintronics. Thus, to find new half-semiconducting materials is highly desirable. …

[Phys. Rev. B 108, 184413] Published Thu Nov 16, 2023

Floquet codes and phases in twist-defect networks
Joseph Sullivan, Rui Wen, and Andrew C. Potter
Author(s): Joseph Sullivan, Rui Wen, and Andrew C. Potter

We introduce a class of models, dubbed paired twist-defect networks, that generalize the structure of Kitaev's honeycomb model for which there is a direct equivalence between: (i) Floquet codes (FCs), (ii) adiabatic loops of gapped Hamiltonians, and (iii) unitary loops or Floquet-enriched topologica…

[Phys. Rev. B 108, 195134] Published Thu Nov 16, 2023

Acoustic higher-order topological insulators protected by multipole chiral numbers
Yuzeng Li, Huahui Qiu, Qicheng Zhang, and Chunyin Qiu
Author(s): Yuzeng Li, Huahui Qiu, Qicheng Zhang, and Chunyin Qiu

Higher-order topological insulators, which go beyond the conventional bulk-boundary correspondence, have been attracting extensive interest in past years. Very recently, it was pointed out that chiral-symmetric higher-order topological insulators can be characterized by a $\mathbb{Z}$ topological in…

[Phys. Rev. B 108, 205135] Published Thu Nov 16, 2023

Found 1 papers in prl
Date of feed: Fri, 17 Nov 2023 04:17:15 GMT

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

Non–Pauli Errors Can Be Efficiently Sampled in Qudit Surface Codes
Yue Ma, Michael Hanks, and M. S. Kim
Author(s): Yue Ma, Michael Hanks, and M. S. Kim

Surface codes are the most promising candidates for fault-tolerant quantum computation. Single qudit errors are typically modeled as Pauli operators, to which general errors are converted via randomizing methods. In this Letter, we quantify remaining correlations after syndrome measurement for a qud…

[Phys. Rev. Lett. 131, 200602] Published Thu Nov 16, 2023

Found 1 papers in pr_res
Date of feed: Fri, 17 Nov 2023 04:17:13 GMT

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

Field-induced Berry connection and anomalous planar Hall effect in tilted Weyl semimetals
YuanDong Wang, Zhen-Gang Zhu, and Gang Su
Author(s): YuanDong Wang, Zhen-Gang Zhu, and Gang Su

We propose the linear and nonlinear anomalous planar Hall effect (APHE) in tilted Weyl semimetals in the presence of an in-plane magnetic and electric field, where the field-induced Berry connection plays a key role. The conductivity of linear APHE is ascribed to the quantum metric and is antisymmet…

[Phys. Rev. Research 5, 043156] Published Thu Nov 16, 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]+)|(flatband)|(flat.{1}band)|(LK.{1}99)

Enhanced optical conductivity and many-body effects in strongly-driven photo-excited semi-metallic graphite
< author missing >

Found 1 papers in scipost

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

Topological interface states -- a possible path towards a Landau-level laser in the THz regime, by Mark O. Goerbig
< author missing >
Submitted on 2023-11-16, refereeing deadline 2023-11-30.