Found 69 papers in cond-mat
Date of feed: Tue, 24 Oct 2023 00:30:00 GMT

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Optimized Analysis of the AC Magnetic Susceptibility Data in Several Spin-Glass Systems using the Vogel-Fulcher and Power Laws. (arXiv:2310.13706v1 [cond-mat.dis-nn])
Mouli Roy-Chowdhury, Mohindar S. Seehra, Subhash Thota

In spin-glasses (SG), the relaxation time $\tau$ ($= 1/2{\pi}f$) vs. $T_f$ data at the peak position $T_f$ in the temperature variation of the ac magnetic susceptibilities at different frequencies f is often fit to the Vogel-Fulcher Law (VFL): $\tau=\tau_0\exp[E_a/k_b(T_f-T_0)]$ and to the Power Law (PL): $\tau = \tau_0^*[(T_f-T_{SG}/T_{SG}]^{-z\nu}$. Both these laws have three fitting parameters each, leaving a degree of uncertainty since the magnitudes of the evaluated parameters $\tau_0$, $E_a/k_B$, $\tau_{0^*}$ and $z\nu$ depend strongly on the choice of $T_0$ and $T_{SG}$. Here we report an optimized procedure for the analysis of $\tau$ vs. $T_f$ data on several SG systems for which we could extract such data from published sources. In this optimized method, the data of $\tau$ vs. $T_f$ are fit by varying $T_0$ in the linear plots of $\ln \tau$ vs $1/ (T_f - T_0)$ for the VFL and by varying $T_{SG}$ in the linear plot of $\ln \tau$ vs. $\ln (T_f - T_{SG})/ T_{SG}$ for the PL till optimum fits are obtained. The analysis of the associated magnitudes of $\tau_0$, $E_a/k_B$, $\tau_{0^*}$ and $z\nu$ for these optimum values of $T_0$ and $T_{SG}$ shows that magnitudes of $\tau_{0^*}$, $\tau_0$ and $z\nu$ fail to provide a clear distinction between canonical and cluster SG. However, new results emerge showing $E_a/(k_BT_0) < 1$ in canonical SG whereas $E_a/(k_BT_0) >1$ for cluster SG systems and the optimized $T_0 <$ optimized $T_{SG}$ in all cases. Although some interpretation of these new results is presented, a more rigorous theoretical justification of the boundary near $E_a/(k_BT_0) \sim 1$ is desired along with testing of these criteria in other SG systems.


Boundary conditions, phase distribution and hidden symmetry in 1D localization. (arXiv:2310.13726v1 [cond-mat.dis-nn])
I. M. Suslov (P.L.Kapitza Institute for Physical Problems, 119334 Moscow, Russia)

One-dimensional disordered systems with a random potential of a small amplitude and short-range correlations are considered near the initial band edge. The evolution equation is obtained for the mutual ditribution P(\rho,\psi) of the Landauer resistance \rho and the phase variable \psi=\theta-\varphi (\theta and \varphi are phases entering the transfer matrix), when the system length L is increased. In the large L limit, the equation allows separation of variables, which provides the existence of the stationary distribution P(\psi), determinative the coefficients in the evolution equation for P(\rho). The limiting distribution P(\rho) for L\to\infty is log-normal and does not depend on boundary conditions. It is determined by the 'internal' phase distribution, whose form is established in the whole energy range including the forbidden band of the initial crystal. The random phase approximation is valid in the deep of the allowed band, but strongly violated for other energies. The phase \psi appears to be a 'bad' variable, while the 'correct' vaiable is \omega=-ctg (psi/2). The form of the stationary distribution P(\omega) is determined by the internal properties of the system and is independent of boundary conditions. Variation of the boundary conditions leads to the scale transformation \omega\to s\omega and translations \omega \to \omega+\omega_0 and \psi\to\psi+\psi_0, which determinates the 'external' phase distribution, entering the evolution equations. Independence of the limiting distribution P(\rho) on the external distribution P(\psi) allows to say on the hidden symmetry, whose character is revealed below.


On quantum melting of superfluid vortex crystals: from Lifshitz scalar to dual gravity. (arXiv:2310.13741v1 [cond-mat.quant-gas])
Dung Xuan Nguyen, Sergej Moroz

Despite a long history of studies of vortex crystals in rotating superfluids, their melting due to quantum fluctuations is poorly understood. Here we develop a fracton-elasticity duality to investigate a two-dimensional vortex lattice within the fast rotation regime, where the Lifshitz model of the collective Tkachenko mode serves as the leading-order low-energy effective theory. We incorporate topological defects and discuss several quantum melting scenarios triggered by their proliferation. Furthermore, we lay the groundwork for a dual non-linear gravity description of the superfluid vortex crystals.


Designing Moir\'e Patterns by Bending. (arXiv:2310.13743v1 [cond-mat.mes-hall])
Pierre A. Pantaleón, Héctor Sainz-Cruz, Francisco Guinea

Motivated by a recent experiment [Kapfer et. al., Science 381, 677 (2023)], we analyze the low-energy physics of a bent nanoribbon placed on top of graphene, which creates a gradually changing moir\'e pattern. By means of a classical elastic model we derive the strains in the ribbon and we obtain its spectrum with a scaled tight-binding model. In a nanoribbon on a substrate pushed at one edge, the interplay between elasticity and van der Waals forces lead to a quasi-universal shape, with a well defined maximum twist angle, irrespective of the force applied at the end. Near the clamped edge, strong strains and small angles leads to one-dimensional channels. Near the bent edge, a long region behaves like magic angle twisted bilayer graphene (TBG), showing a sharp peak in the density of states, mostly isolated from the rest of the spectrum. We also calculate the band topology along the ribbon and we find that it is stable for large intervals of strains an twist angles. Together with the experimental observations, these results show that the bent nanoribbon geometry is ideal for exploring superconductivity and correlated phases in TBG in the very sought-after regime of ultra-low twist angle disorder.


Quantum vortex lattice via Lifshitz duality. (arXiv:2310.13794v1 [cond-mat.str-el])
Yi-Hsien Du, Ho Tat Lam, Leo Radzihovsky

We study an effective field theory of a vortex lattice in a two-dimensional neutral rotating superfluid. Utilizing particle-vortex dualities we explore its formulation in terms of a $U(1)$ gauge theory coupled to elasticity, that at low energies reduces to a Lifshitz theory augmented with a Berry phase term encoding the vortex dynamics in the presence of a superflow. Utilizing elasticity- and Lifshitz-gauge theory dualities, we derive dual formulations of the vortex lattice in terms of a traceless symmetric scalar-charge theory and demonstrate low-energy equivalence of our dual gauge theory to its elasticity-gauge theory dual. We further discuss a multipole symmetry of the vortex lattice and its dual gauge theory's multipole one-form symmetries. We also study its topological crystalline defects, where the multipole one-form symmetry plays a prominent role, organizing the defects, explaining their restricted mobility, and characterizing descendant vortex phases.


Ultralow lattice thermal transport and considerable wave-like phonon tunneling in chalcogenide perovskite BaZrS$_3$. (arXiv:2310.13851v1 [cond-mat.mtrl-sci])
Yu Wu, Ying Chen, Qiaoqiao Li, Kui Xue, Hezhu Shao, Hao Zhang, Liujiang Zhou

Chalcogenide perovskites provide a promising avenue for non-toxic, stable thermoelectric materials. Here, thermal transport and thermoelectric properties of BaZrS$_3$ as a typical orthorhombic perovskite are investigated. An extremely low lattice thermal conductivity $\kappa_L$ of 1.84 W/mK at 300 K is revealed for BaZrS$_3$, due to the softening effect of Ba atoms on the lattice and the strong anharmonicity caused by the twisted structure. We demonstrate that coherence contributions to $\kappa_L$, arising from wave-like phonon tunneling, leading to a 18 \% thermal transport contribution at 300 K. The increasing temperature softens the phonons, thus reducing the group velocity of materials and increasing the scattering phase space. However, it simultaneously reduces the anharmonicity, which is dominant in BaZrS$_3$ and ultimately improves the particle-like thermal transport. Further, by replacing S atom with Se and Ti-alloying strategy, $ZT$ value of BaZrS$_3$ is significantly increased from 0.58 to 0.91 at 500 K, making it an important candidate for thermoelectric applications.


Symmetry-dependent dielectric screening of optical phonons in monolayer graphene. (arXiv:2310.13868v1 [cond-mat.mes-hall])
Loïc Moczko, Sven Reichardt, Aditya Singh, Xin Zhang, Luis E. Parra López, Joanna L. P. Wolff, Aditi Raman Moghe, Etienne Lorchat, Rajendra Singh, Kenji Watanabe, Takashi Taniguchi, Hicham Majjad, Michelangelo Romeo, Arnaud Gloppe, Ludger Wirtz, Stéphane Berciaud

Quantised lattice vibrations (i.e., phonons) in solids are robust and unambiguous fingerprints of crystal structures and of their symmetry properties. In metals and semimetals, strong electron-phonon coupling may lead to so-called Kohn anomalies in the phonon dispersion, providing an image of the Fermi surface in a non-electronic observable. Kohn anomalies become prominent in low-dimensional systems, in particular in graphene, where they appear as sharp kinks in the in-plane optical phonon branches. However, in spite of intense research efforts on electron-phonon coupling in graphene and related van der Waals heterostructures, little is known regarding the links between the symmetry properties of optical phonons at and near Kohn anomalies and their sensitivity towards the local environment. Here, using inelastic light scattering (Raman) spectroscopy, we investigate a set of custom-designed graphene-based van der Waals heterostructures, wherein dielectric screening is finely controlled at the atomic layer level. We demonstrate experimentally and explain theoretically that, depending exclusively on their symmetry properties, the two main Raman modes of graphene react differently to the surrounding environment. While the Raman-active near-zone-edge optical phonons in graphene undergo changes in their frequencies due to the neighboring dielectric environment, the in-plane, zone-centre optical phonons are symmetry-protected from the influence of the latter. These results shed new light on the unique electron-phonon coupling properties in graphene and related systems and provide invaluable guidelines to characterise dielectric screening in van der Waals heterostructures and moir\'e superlattices.


Advances in Complex Oxide Quantum Materials Through New Approaches to Molecular Beam Epitaxy. (arXiv:2310.13902v1 [cond-mat.mtrl-sci])
Gaurab Rimal, Ryan B. Comes

Molecular beam epitaxy (MBE), a workhorse of the semiconductor industry, has progressed rapidly in the last few decades in the development of novel materials. Recent developments in condensed matter and materials physics have seen the rise of many novel quantum materials that require ultra-clean and high-quality samples for fundamental studies and applications. Novel oxide-based quantum materials synthesized using MBE have advanced the development of the field and materials. In this review, we discuss the recent progress in new MBE techniques that have enabled synthesis of complex oxides that exhibit "quantum" phenomena, including superconductivity and topological electronic states. We show how these techniques have produced breakthroughs in the synthesis of 4d and 5d oxide films and heterostructures that are of particular interest as quantum materials. These new techniques in MBE offer a bright future for the synthesis of ultra-high quality oxide quantum materials.


Quantum theory of the magnetochiral anisotropy coefficient in ZrTe$_5$. (arXiv:2310.13909v1 [cond-mat.mes-hall])
Yi-Xiang Wang, Fuxiang Li

Recent experiments performed the nonreciprocal magneotransport in ZrTe$_5$ and obtained a giant magnetochiral anisotropy (MCA) coefficient $\gamma'$. The existing theoretical analysis was based on the semiclassical Boltzmann equation. In this paper, we develop a full quantum theory to calculate $\gamma'$. We reveal that the $xz$-mirror symmetry breaking term also breaks the parity symmetry of the system, and leads to the mixed selection rules and a nonvanishing second-order conductivity $\sigma_{xxx}$. The calculations show that $\gamma'$ decreases with the magnetic field, survives only to weak impurity scatterings, and grows almost linearly with the strength of the $xz$-mirror symmetry breaking. Our paper can provide a deeper insight into the intrinsic nonreciprocal magnetotransport phenomena in the topological semimetal material.


Valley polarization and photocurrent generation in transition metal dichalcogenide alloy MoS$_{2x}$Se$_{2(1-x)}$. (arXiv:2310.13924v1 [cond-mat.mes-hall])
Chumki Nayak, Suvadip Masanta, Sukanya Ghosh, Shubhadip Moulick, Atindra Nath Pal, Indrani Bose, Achintya Singha

Monolayer transition metal dichalcogenides (TMDCs) constitute the core group of materials in the emerging semiconductor technology of valleytronics. While the coupled spin-valley physics of pristine TMDC materials and their heterstructures has been extensively investigated, less attention was given to TMDC alloys, which could be useful in optoelectronic applications due to the tunability of their band gaps. We report here our experimental investigations of the spin-valley physics of the monolayer and bilayer TMDC alloy, MoS$_{2x}$Se$_{2(1-x)}$, in terms of valley polarization and the generation as well as electrical control of a photocurrent utilising the circular photogalvanic effect. Piezoelectric force microscopy provides evidence for an internal electric field perpendicular to the alloy layer, thus breaking the out-of-plane mirror symmetry. This feature allows for the generation of a photocurrent in the alloy bilayer even in the absence of an external electric field. A comparison of the photocurrent device, based on the alloy material, is made with similar devices involving other TMDC materials.


Character of electronic states in the transport gap of molecules on surfaces. (arXiv:2310.13962v1 [cond-mat.mes-hall])
Abhishek Grewal, Christopher C. Leon, Klaus Kuhnke, Klaus Kern, Olle Gunnarsson

We report on scanning tunneling microscopy (STM) topographs of individual metal phthalocyanines (MPc) on a thin salt (NaCl) film on a gold substrate, at tunneling energies within the molecule's electronic transport gap. Theoretical models of increasing complexity are discussed. The calculations for MPcs adsorbed on a thin NaCl layer on Au(111) demonstrate that the STM pattern rotates with the molecule's orientations - in excellent agreement with the experimental data. Thus, even the STM topography obtained for energies in the transport gap represent the structure of a one atom thick molecule. It is shown that the electronic states inside the transport gap can be rather accurately approximated by linear combinations of bound molecular orbitals (MOs). The gap states include not only the frontier orbitals but also surprisingly large contributions from energetically much lower MOs. These results will be essential for understanding processes, such as exciton creation, which can be induced by electrons tunneling through the transport gap of a molecule.


The Emergence of Anisotropic Superconductivity in the Nodal-line Semi-metal TlTaSe2. (arXiv:2310.13986v1 [cond-mat.supr-con])
Mukhtar Lawan Adam, Ibrahim Buba Garba, Sulaiman Muhammad Gana, Bala Ismail Adamu, Abba Alhaji Bala, Abdulsalam Aji Suleiman, Ahmad Hamisu, Tijjani Hassan Darma, Auwal Musa, Abdulkadir S. Gidado

TlTaSe2 is a non-centrosymmetric quasi-2D crystal semi-metal hosting nodal-line topological features protected by mirror-reflection symmetry. Here, we investigated the superconducting properties of TlTaSe2 using the first-principles anisotropic Migdal-Eliashberg theory. The Fermi surface hosts well gapped multiband features contributed by the Ta 5d and Tl 6p orbitals. Moreso, anisotropic superconducting gaps were found to exist at 2.15 and 4.5 meV around the in-plane orbitals, coupling effectively with the in-plane phonons of the Ta and Tl atoms. Using the Allen-Dynes-modified McMillan formula, we found a superconducting transition temperature of 6.67 K, accompanied by a robust electron-phonon coupling constant {\lambda} of 0.970. This investigation provides valuable insights into the mechanisms underlying anisotropic superconductivity in TlTaSe2.


Topological Magnetoresistance of Magnetic Skyrmionic Bubbles. (arXiv:2310.13997v1 [cond-mat.mtrl-sci])
Fei Li, Hao Nie, Yu Zhao, Zhihe Zhao, Juntao Huo, Hongxian Shen, Sida Jiang, Renjie Chen, Aru Yan, S-W Cheong, Weixing Xia, Lunyong Zhang, Jianfei Sun

Magnetic skyrmions offer promising prospects for constructing future energy-efficient and high-density information technology, leading to extensive explorations of new skyrmionic materials recently. The topological Hall effect has been widely adopted as a distinctive marker of skyrmion emergence. Alternately, here we propose a novel signature of skyrmion state by quantitatively investigating the magnetoresistance (MR) induced by skyrmionic bubbles in CeMn2Ge2. An intriguing finding was revealed: the anomalous MR measured at different temperatures can be normalized into a single curve, regardless of sample thickness. This behavior can be accurately reproduced by the recent chiral spin textures MR model. Further analysis of the MR anomaly allowed us to quantitatively examine the effective magnetic fields of various scattering channels. Remarkably, the analyses, combined with the Lorentz transmission electronic microscopy results, indicate that the in-plane scattering channel with triplet exchange interactions predominantly governs the magnetotransport in the Bloch-type skyrmionic bubble state. Our results not only provide insights into the quantum correction on MR induced by skyrmionic bubble phase, but also present an electrical probing method for studying chiral spin texture formation, evolution and their topological properties, which opens up exciting possibilities for identifying new skyrmionic materials and advancing the methodology for studying chiral spin textures.


Topological phases induced by charge fluctuations in Majorana wires. (arXiv:2310.14035v1 [cond-mat.mes-hall])
M. S. Shustin, S. V. Aksenov, I. S. Burmistrov

One of the problems concerning topological phases in solid-state systems which still remains urgent is an issue of many-body effects. In this study we address it within perturbative theory framework by considering topological phase transitions related to charge correlations in the extended Kitaev chain model that belongs to the BDI symmetry class. Obtained corrections to a zero-frequency quasiparticle Green's function allow to separate the mean-field and fluctuation contributions to a total winding number. As a result, the phase transitions caused solely by the latter are unveiled. We thoroughly analyze the mechanism of such transitions in terms of fluctuation-induced nodal points and spectrum renormalization. Additionally, features of other quasiparticle properties such as effective mass and damping are discussed in the context of topological phase transitions.


Anionic Character of the Conduction Band of Sodium Chloride. (arXiv:2310.14070v1 [cond-mat.mtrl-sci])
Christopher C. Leon, Abhishek Grewal, Klaus Kuhnke, Klaus Kern, Olle Gunnarsson

The alkali halides are ionic compounds. Each alkali atom donates an electron to a halogen atom, leading to ions with full shells. The valence band is mainly located on halogen atoms, while, in a traditional picture, the conduction band is mainly located on alkali atoms. Scanning tunnelling microscopy of NaCl at 4 K actually shows that the conduction band is located on Cl$^-$ because the strong Madelung potential reverses the order of the Na$^+$ 3s and Cl$^-$ 4s levels. We verify this reversal is true for both atomically thin and bulk NaCl, and discuss implications for II-VI and I-VII compounds.


Localization renormalization and quantum Hall systems. (arXiv:2310.14074v1 [cond-mat.mes-hall])
Bartholomew Andrews, Dominic Reiss, Fenner Harper, Rahul Roy

The obstruction to constructing localized degrees of freedom is a signature of several interesting condensed matter phases. We introduce a localization renormalization procedure that harnesses this property, and apply our method to distinguish between topological and trivial phases in quantum Hall and Chern insulators. By iteratively removing a fraction of maximally-localized orthogonal basis states, we find that the localization length in the residual Hilbert space exhibits a power-law divergence as the fraction of remaining states approaches zero, with an exponent of $\nu=0.5$. In sharp contrast, the localization length converges to a system-size-independent constant in the trivial phase. We verify this scaling using a variety of algorithms to truncate the Hilbert space, and show that it corresponds to a statistically self-similar expansion of the real-space projector. This result accords with a renormalization group picture and motivates the use of localization renormalization as a versatile numerical diagnostic for quantum Hall insulators.


Bound states and local topological phase diagram of classical impurity spins coupled to a Chern insulator. (arXiv:2310.14097v1 [cond-mat.mes-hall])
Simon Michel, Axel Fünfhaus, Robin Quade, Roser Valentí, Michael Potthoff

The existence of bound states induced by local impurities coupled to an insulating host depends decisively on the global topological properties of the host's electronic structure. In this context, we consider magnetic impurities modelled as classical unit-length spins that are exchange-coupled to the spinful Haldane model on the honeycomb lattice. We investigate the spectral flow of bound states with the coupling strength $J$ in both the topologically trivial and Chern-insulating phases. In addition to conventional $k$-space topology, an additional, spatially local topological feature is available, based on the space of impurity-spin configurations forming, in case of $R$ impurities, an $R$-fold direct product of two-dimensional spheres. Global $k$-space and local $S$-space topology are represented by different topological invariants, the first ($k$-space) Chern number and the $R$-th ($S$-space) spin-Chern number. We demonstrate that there is a local $S$-space topological transition as a function of $J$ associated with a change in the spin Chern number and work out the implications of this for the $J$-dependent local electronic structure close to the impurities and, in particular, for in-gap bound states. The critical exchange couplings' dependence on the parameters of the Haldane model, and thus on the $k$-space topological state, is obtained numerically to construct local topological phase diagrams for systems with $R=1$ and $R=2$ impurity spins.


Properties of an {\alpha}-T3 Aharonov-Bohm quantum ring: Interplay of Rashba spin-orbit coupling and topological defect. (arXiv:2310.14169v1 [cond-mat.mes-hall])
Mijanur Islam, Saurabh Basu

In this paper we investigate the interplay of the Rashba spin-orbit coupling (RSOC) and a topological defect, such as a screw dislocation in an {\alpha}-T3 Aharonov-Bohm quantum ring and scrutinized the effect of an external transverse magnetic field therein. Our study reveals that the energy spectrum follows a parabolic dependence on the Burgers vector associated with the screw dislocation. Moreover, its presence results in an effective flux, encompassing the ramifications due to both the topological flux and that due to the external magnetic field. Furthermore, we observe periodic oscillations in the persistent current in both charge and spin sectors, with a period equal to one flux quantum, which, however suffers a phase shift that is proportional to the dislocation present in the system. Such tunable oscillations of the spin persistent current highlights potential application of our system to be used as spintronic devices. Additionally, we derive and analyse the thermodynamic properties of the ring via obtaining the canonical partition function through Euler-Maclaurin formula. In particular, we compute the thermodynamic potentials, free energies, entropy, and heat capacity and found the latter to yield the expected Dulong-Petit law at large temperatures.


Carrier doping of Bi$_2$Se$_3$ surface by chemical adsorption -- a DFT study. (arXiv:2310.14177v1 [cond-mat.mtrl-sci])
Cheng Fan, Kazuyuki Sakamoto, Peter Krüger

Bi$_2$Se$_3$ is one of the most promising topological insulators, but it suffers from intrinsic n-doping due to Se-vacancies, which shifts the Fermi level into the bulk conduction band, leading to topologically trivial carriers. Recently it was shown that this Fermi-level shift can be compensated by a locally controlled surface p-doping process, through water adsorption and XUV irradiation. Here, the microscopic mechanism of this surface doping is studied by means of density functional theory (DFT) focusing on the adsorption of H$_2$O, OH, O, C and CH on Bi$_2$Se$_3$. We find that water adsorption has a negligible doping effect while hydroxyl groups lead to n-doping. Carbon adsorption on Se vacancies gives rise to p-doping but it also strongly modifies the electronic band structure around the Dirac point. Only if the Se vacancies are filled with atomic oxygen, the experimentally observed p-doping without change of the topological surface bands is reproduced. Based on the DFT results, we propose a reaction path where photon absorption gives rise to water splitting and the produced O atoms fill the Se vacancies. Adsorbed OH groups appear as intermediate states and carbon impurities may have a catalytic effect in agreement with experimental observations.


Multi-charged moments and symmetry-resolved R\'enyi entropy of free compact boson for multiple disjoint intervals. (arXiv:2310.14186v1 [hep-th])
Himanshu Gaur, Urjit A. Yajnik

We study multi-charged moments and symmetry-resolved R\'enyi entropy of free compact boson for multiple disjoint intervals. The R\'enyi entropy evaluation involves computing the partition function of the theory on Riemann surfaces with genus g>1. This makes R\'enyi entropy sensitive to the local conformal algebra of the theory. The free compact boson possesses a global U(1) symmetry with respect to which we resolve R\'enyi entropy. The multi-charged moments are obtained by studying the correlation function of flux-generating vertex operators on the associated Riemann surface. Symmetry-resolved R\'enyi entropy is then obtained from the Fourier transforms of the charged moments. R\'enyi entropy is shown to have the familiar equipartition into local charge sectors up to the leading order. The multi-charged moments are also essential in studying the symmetry resolution of mutual information. The multi-charged moments of the self-dual compact boson and massless Dirac fermion are also shown to match for the cases when the associated reduced density matrix moments are known to be the same. Finally, we numerically check our results against the tight-binding model.


Controlling spin-orbit coupling to tailor type-II Dirac bands. (arXiv:2310.14202v1 [cond-mat.mtrl-sci])
Nguyen Huu Lam, Phuong Lien Nguyen, Byoung Ki Choi, Trinh Thi Ly, Ganbat Duvjir, Tae Gyu Rhee, Yong Jin Jo, Tae Heon Kim, Chris Jozwiak, Aaron Bostwick, Eli Rotenberg, Younghun Hwang, Young Jun Chang, Jaekwang Lee, Jungdae Kim

NiTe2, a type-II Dirac semimetal with strongly tilted Dirac band, has been explored extensively to understand its intriguing topological properties. Here, using density-functional theory (DFT) calculations, we report that the strength of spin-orbit coupling (SOC) in NiTe2 can be tuned by Se substitution. This results in negative shifts of the bulk Dirac point (BDP) while preserving the type-II Dirac band. Indeed, combined studies using scanning tunneling spectroscopy (STS) and angle-resolved photoemission spectroscopy (ARPES) confirm that the BDP in the NiTe2-xSex alloy moves from +0.1 eV (NiTe2) to -0.3 eV (NiTeSe) depending on the Se concentrations, indicating the effective tunability of type-II Dirac fermions. Our results demonstrate an approach to tailor the type-II Dirac band in NiTe2 by controlling the SOC strength via chalcogen substitution. This approach can be applicable to different types of topological materials.


Real-space formulation of topology for disordered Rice-Mele chains without chiral symmetry. (arXiv:2310.14204v1 [cond-mat.mes-hall])
Kiminori Hattori, Ata Yamaguchi

In this paper, we derive a real-space topological invariant that involves all energy states in the system. This global invariant, denoted by $Q$, is always quantized to be 0 or 1, independent of symmetries. In terms of $Q$, we numerically investigate topological properties of the nonchiral Rice-Mele model including random onsite potentials to show that nontrivial bulk topology is sustained for weak enough disorder. In this regime, a finite spectral gap persists, and then $Q$ is definitely identified. We also consider sublattice polarization of disorder potentials. In this case, the energy spectrum retains a gap regardless of disorder strength so that $Q$ is unaffected by disorder. This implies that bulk topology remains intact as long as the spectral gap opens.


Machine-learning-assisted analysis of transition metal dichalcogenide thin-film growth. (arXiv:2310.14205v1 [cond-mat.mtrl-sci])
Hyuk Jin Kim, Minsu Chong, Tae Gyu Rhee, Yeong Gwang Khim, Min-Hyoung Jung, Young-Min Kim, Hu Young Jeong, Byoung Ki Choi, Young Jun Chang

In situ reflective high-energy electron diffraction (RHEED) is widely used to monitor the surface crystalline state during thin-film growth by molecular beam epitaxy (MBE) and pulsed laser deposition. With the recent development of machine learning (ML), ML-assisted analysis of RHEED videos aids in interpreting the complete RHEED data of oxide thin films. The quantitative analysis of RHEED data allows us to characterize and categorize the growth modes step by step, and extract hidden knowledge of the epitaxial film growth process. In this study, we employed the ML-assisted RHEED analysis method to investigate the growth of 2D thin films of transition metal dichalcogenides (ReSe2) on graphene substrates by MBE. Principal component analysis (PCA) and K-means clustering were used to separate statistically important patterns and visualize the trend of pattern evolution without any notable loss of information. Using the modified PCA, we could monitor the diffraction intensity of solely the ReSe2 layers by filtering out the substrate contribution. These findings demonstrate that ML analysis can be successfully employed to examine and understand the film-growth dynamics of 2D materials. Further, the ML-based method can pave the way for the development of advanced real-time monitoring and autonomous material synthesis techniques.


Atomic arrangement of van der Waals heterostructures using X-ray scattering and crystal truncation rod analysis. (arXiv:2310.14207v1 [cond-mat.mtrl-sci])
Ryung Kim, Byoung Ki Choi, Kyeong Jun Lee, Hyuk Jin Kim, Hyun Hwi Lee, Tae Gyu Rhee, Yeong Gwang Khim, Young Jun Chang, Seo Hyoung Chang

Vanadium diselenide (VSe2) has intriguing physical properties such as unexpected ferromagnetism at the two-dimensional limit. However, the experimental results for room temperature ferromagnetism are still controversial and depend on the detailed crystal structure and stoichiometry. Here we introduce crystal truncation rod (CTR) analysis to investigate the atomic arrangement of bilayer VSe2 and bilayer graphene (BLG) hetero-structures grown on a 6H-SiC(0001) substrate. Using non-destructive CTR analysis, we were able to obtain electron density profiles and detailed crystal structure of the VSe2/BLG heterostructures. Specifically, the out-of-plane lattice parameters of each VSe2 layer were modulated by the interface compared to that of the bulk VSe2 1T phase. The atomic arrangement of the VSe2/BLG heterostructure provides deeper understanding and insight for elucidating the magnetic properties of the van der Waals heterostructure.


Topologically Variable and Volumetric Morphing of 3D Architected Materials with Shape Locking. (arXiv:2310.14220v1 [cond-mat.mtrl-sci])
Kai Xiao, Yuhao Wang, Chao Song, Bihui Zou, Zihe Liang, Heeseung Han, Yilin Du, Hanqing Jiang, Jaehyung Ju

The morphing of 3D structures is suitable for i) future tunable material design for customizing material properties and ii) advanced manufacturing tools for fabricating 3D structures on a 2D plane. However, there is no inverse design method for topologically variable and volumetric morphing or morphing with shape locking, which limits practical engineering applications. In this study, we construct a general inverse design method for 3D architected materials for topologically variable and volumetric morphing, whose shapes are lockable in the morphed states, which can contribute to future tunable materials, design, and advanced manufacturing. Volumetric mapping of bistable unit cells onto any 3D morphing target geometry with kinematic and kinetic modifications can produce flat-foldable and volumetric morphing structures with shape-locking. This study presents a generalized inverse design method for 3D metamaterial morphing that can be used for structural applications with shape locking. Topologically variable morphing enables the manufacture of volumetric structures on a 2D plane, saving tremendous energy and materials compared with conventional 3D printing. Volumetric morphing can significantly expand the design space with tunable physical properties without limiting the selection of base materials.


Investigation of the mechanism of the anomalous Hall effects in Cr2Te3/(BiSb)2(TeSe)3 heterostructure. (arXiv:2310.14259v1 [cond-mat.mtrl-sci])
Seong Won Cho, In Hak Lee, Youngwoong Lee, Sangheon Kim, Yeong Gwang Khim, Seung-Young Park, Younghun Jo, Junwoo Choi, Seungwu Han, Young Jun Chang, Suyoun Lee

The interplay between ferromagnetism and the non-trivial topology has unveiled intriguing phases in the transport of charges and spins. For example, it is consistently observed the so-called topological Hall effect (THE) featuring a hump structure in the curve of the Hall resistance (Rxy) vs. a magnetic field (H) of a heterostructure consisting of a ferromagnet (FM) and a topological insulator (TI). The origin of the hump structure is still controversial between the topological Hall effect model and the multi-component anomalous Hall effect (AHE) model. In this work, we have investigated a heterostructure consisting of BixSb2-xTeySe3-y (BSTS) and Cr2Te3 (CT), which are well-known TI and two-dimensional FM, respectively. By using the so-called minor-loop measurement, we have found that the hump structure observed in the CT/BSTS is more likely to originate from two AHE channels. Moreover, by analyzing the scaling behavior of each amplitude of two AHE with the longitudinal resistivities of CT and BSTS, we have found that one AHE is attributed to the extrinsic contribution of CT while the other is due to the intrinsic contribution of BSTS. It implies that the proximity-induced ferromagnetic layer inside BSTS serves as a source of the intrinsic AHE, resulting in the hump structure explained by the two AHE model.


Superconductivity in the high-entropy ceramics Ti0.2Zr0.2Nb0.2Mo0.2Ta0.2Cx with possible nontrivial band topology. (arXiv:2310.14271v1 [cond-mat.supr-con])
Lingyong Zeng, Xunwu Hu, Yazhou Zhou, Mebrouka Boubeche, Ruixin Guo, Yang Liu, Si-Chun Luo, Shu Guo, Kuan Li, Peifeng Yu, Chao Zhang, Wei-Ming Guo, Liling Sun, Dao-Xin Yao, Huixia Luo

Topological superconductors have drawn significant interest from the scientific community due to the accompanying Majorana fermions. Here, we report the discovery of electronic structure and superconductivity in high-entropy ceramics Ti0.2Zr0.2Nb0.2Mo0.2Ta0.2Cx (x = 1 and 0.8) combined with experiments and first-principles calculations. The Ti0.2Zr0.2Nb0.2Mo0.2Ta0.2Cx high-entropy ceramics show bulk type-II superconductivity with Tc about 4.00 K (x = 1) and 2.65 K (x = 0.8), respectively. The specific heat jump is equal to 1.45 (x = 1) and 1.52 (x = 0.8), close to the expected value of 1.43 for the BCS superconductor in the weak coupling limit. The high-pressure resistance measurements show that a robust superconductivity against high physical pressure in Ti0.2Zr0.2Nb0.2Mo0.2Ta0.2C, with a slight Tc variation of 0.3 K within 82.5 GPa. Furthermore, the first-principles calculations indicate that the Dirac-like point exists in the electronic band structures of Ti0.2Zr0.2Nb0.2Mo0.2Ta0.2C, which is potentially a topological superconductor. The Dirac-like point is mainly contributed by the d orbitals of transition metals M and the p orbitals of C. The high-entropy ceramics provide an excellent platform for the fabrication of novel quantum devices, and our study may spark significant future physics investigations in this intriguing material.


On the dilemma between percolation processes and fluctuating pairs as the origin of the enhanced conductivity above the superconducting transition in cuprates. (arXiv:2310.14284v1 [cond-mat.supr-con])
I. F. Llovo, J. Mosqueira, F. Vidal

The confrontation between percolation processes and superconducting fluctuations to account for the observed enhanced in-plane electrical conductivity above but near $T_c$ in cuprates is revisited. The cuprates studied here, La$_{1.85}$Sr$_{0.15}$CuO$_4$, Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$, and Tl$_2$Ba$_2$Ca$_2$Cu$_3$O$_{10}$, have a different number of superconducting CuO$_2$ layers per unit-cell length and different Josephson coupling between them, and are optimally-doped to minimize $T_c$-inhomogeneities. The excellent chemical and structural quality of these samples also contribute to minimize the effect of extrinsic $T_c$-inhomogeneities, a crucial aspect when analyzing the possible presence of intrinsic percolative processes. Our analyses also cover the so-called high reduced-temperature region, up to the resistivity rounding onset $\varepsilon_{onset}$. By using the simplest form of the effective-medium theory, we show that possible emergent percolation processes alone cannot account for the measured enhanced conductivity. In contrast, these measurements can be quantitatively explained using the Gaussian-Ginzburg-Landau (GGL) approach for the effect of superconducting fluctuations in layered superconductors, extended to $\varepsilon_{onset}$ by including a total energy cutoff, which takes into account the limits imposed by the Heisenberg uncertainty principle to the shrinkage of the superconducting wavefunction. Our analysis confirms the adequacy of this cutoff, and that the effective periodicity length is controlled by the relative Josephson coupling between superconducting layers. These conclusions are reinforced by analyzing one of the recent works that allegedly discards the superconducting fluctuations scenario while supporting a percolative scenario for the enhanced conductivity above $T_c$ in cuprates.


Atomic-Scale Terahertz Near Fields for Ultrafast Tunnelling Spectroscopy. (arXiv:2310.14335v1 [cond-mat.mes-hall])
Vedran Jelic, Stefanie Adams, Mohamed Hassan, Kaedon Cleland-Host, S. Eve Ammerman, Tyler L. Cocker

Lightwave-driven terahertz scanning tunnelling microscopy (THz-STM) is capable of exploring ultrafast dynamics across a wide range of materials with angstrom resolution. In contrast to scanning near-field optical microscopy, where photons scattered by the tip apex are analyzed to access the local dielectric function on the nanoscale, THz-STM uses a strong-field single-cycle terahertz pulse to drive an ultrafast current across a tunnel junction, thereby probing the local density of electronic states. Yet, the terahertz field in a THz-STM junction may also be spectrally modified by the electromagnetic response of the sample. Here, we demonstrate a reliable and self-consistent approach for terahertz near-field waveform acquisition in an atomic tunnel junction that can be generally applied to electrically conductive surfaces. By combining waveform sampling and tailoring with terahertz scanning tunnelling spectroscopy (THz-STS), we comprehensively characterize the tunnel junction and distinguish local sample properties from effects due to terahertz pulse coupling and field enhancement. Through modelling, we verify the presence of an isolated unipolar terahertz-induced current pulse, facilitating straightforward interpretation for differential THz-STS with high spectral resolution. Finally, we demonstrate the feasibility of atomic-scale terahertz time-domain spectroscopy via the extremely localized near-fields in the tunnel junction.


Effects of phylogeny on coexistence in model communities. (arXiv:2310.14392v1 [q-bio.PE])
Carlos A. Servan, Jose A. Capitan, Zachary R. Miller, Stefano Allesina

Species' interactions are shaped by their traits. Thus, we expect traits -- in particular, trait (dis)similarity -- to play a central role in determining whether a particular set of species coexists. Traits are, in turn, the outcome of an eco-evolutionary process summarized by a phylogenetic tree. Therefore, the phylogenetic tree associated with a set of species should carry information about the dynamics and assembly properties of the community. Many studies have highlighted the potentially complex ways in which this phylogenetic information is translated into species' ecological properties. However, much less emphasis has been placed on developing clear, quantitative expectations for community properties under a particular hypothesis.

To address this gap, we couple a simple model of trait evolution on a phylogenetic tree with Lotka-Volterra community dynamics. This allows us to derive properties of a community of coexisting species as a function of the number of traits, tree topology and the size of the species pool. Our analysis highlights how phylogenies, through traits, affect the coexistence of a set of species.

Together, these results provide much-needed baseline expectations for the ways in which evolutionary history, summarized by phylogeny, is reflected in the size and structure of ecological communities.


Collective charge excitations between moir\'e-minibands in twisted WSe2 bilayers from resonant inelastic light scattering. (arXiv:2310.14417v1 [cond-mat.str-el])
Nihit Saigal, Lennart Klebl, Hendrik Lambers, 1Sina Bahmanyar, Veljko Antić, Dante M. Kennes, Tim O. Wehling, Ursula Wurstbauer

We establish low-temperature resonant inelastic light scattering (RILS) spectroscopy as a tool to probe the formation of a series of moir\'e-bands in twisted WSe2 bilayers by accessing collective inter-moir\'e-band excitations (IMBE). We observe resonances in such RILS spectra at energies in agreement with inter-moir\'e band (IMB) transitions obtained from an ab-initio based continuum model. Transitions between the first and second IMB for a twist angle of about 8{\deg} are reported and between first and second, third and higher bands for a twist of about 3{\deg}. The signatures from IMBE for the latter highlight a strong departure from parabolic bands with flat minibands exhibiting very high density of states in accord with theory. These observations allow to quantify the transition energies at the K-point where the states relevant for correlation physics are hosted.


Giant Magnetothermal Conductivity Switching in Semimetallic WSi$_{2}$ Single Crystals. (arXiv:2310.14467v1 [cond-mat.mtrl-sci])
Karl G. Koster, Jackson Hise, Joseph P. Heremans, Joshua E. Goldberger

Materials able to rapidly switch between thermally conductive states by external stimuli such as electric or magnetic fields can be used as all-solid-state thermal switches and open a myriad of applications in heat management, power generation and cooling. Here, we show that the large magnetoresistance that occurs in the highly conducting semimetal $\alpha$-WSi$_{2}$ single crystals leads to dramatically large changes in thermal conductivity at temperatures <100 K. At temperatures <20 K, where electron-phonon scattering is minimized, the thermal conductivity switching ratio between zero field and a 9T applied field can be >7. We extract the electronic and lattice components of the from the thermal conductivity measurements and show that the Lorenz number for this material approximates the theoretical value of L$_{0}$. From the heat capacity and thermal diffusivity, the speed of thermal conductivity switching is estimated to range from 1 x 10$^{-4}$ seconds at 5 K to 0.2 seconds at 100 K for a 5-mm long sample. This work shows that WSi$_{2}$, a highly conducting multi-carrier semimetal, is a promising thermal switch component for low-temperature applications such cyclical adiabatic demagnetization cooling, a technique that would enable replacing $^{3}$He-based refrigerators.


Topological electronic states in holey graphyne. (arXiv:2310.14625v1 [cond-mat.mes-hall])
Yong-Cheng Jiang, Toshikaze Kariyado, Xiao Hu

We unveil that the holey graphyne (HGY), a two-dimensional carbon allotrope where benzene rings are connected by two $-$C$\equiv$C$-$ bonds fabricated recently in a bottom-up way, exhibits topological electronic states. Using first-principles calculations and Wannier tight-binding modeling, we discover a higher-order topological invariant associated with $C_2$ symmetry of the material, and show that the resultant corner modes appear in nanoflakes matching to the structure of precursor reported previously, which are ready for direct experimental observations. In addition, we find that a band inversion between emergent $g$-like and $h$-like orbitals gives rise to a nontrivial topology characterized by $\mathbb{Z}_2$ invariant protected by an energy gap as large as 0.52 eV, manifesting helical edge states mimicking those in the prominent quantum spin Hall effect, which can be accessed experimentally after hydrogenation in HGY. We hope these findings trigger interests towards exploring the topological electronic states in HGY and related future electronics applications.


Reconfigurable Multifunctional van der Waals Ferroelectric Devices and Logic Circuits. (arXiv:2310.14648v1 [cond-mat.mes-hall])
Ankita Ram, Krishna Maity, Cédric Marchand, Aymen Mahmoudi, Aseem Rajan Kshirsagar, Mohamed Soliman, Takashi Taniguchi, Kenji Watanabe, Bernard Doudin, Abdelkarim Ouerghi, Sven Reichardt, Ian O'Connor, Jean-Francois Dayen

In this work, we demonstrate the suitability of Reconfigurable Ferroelectric Field-Effect- Transistors (Re-FeFET) for designing non-volatile reconfigurable logic-in-memory circuits with multifunctional capabilities. Modulation of the energy landscape within a homojunction of a 2D tungsten diselenide (WSe$_2$) layer is achieved by independently controlling two split-gate electrodes made of a ferroelectric 2D copper indium thiophosphate (CuInP$_2$S$_6$) layer. Controlling the state encoded in the Program Gate enables switching between p, n and ambipolar FeFET operating modes. The transistors exhibit on-off ratios exceeding 10$^6$ and hysteresis windows of up to 10 V width. The homojunction can change from ohmic-like to diode behavior, with a large rectification ratio of 10$^4$. When programmed in the diode mode, the large built-in p-n junction electric field enables efficient separation of photogenerated carriers, making the device attractive for energy harvesting applications. The implementation of the Re-FeFET for reconfigurable logic functions shows how a circuit can be reconfigured to emulate either polymorphic ferroelectric NAND/AND logic-in-memory or electronic XNOR logic with long retention time exceeding 10$^4$ seconds. We also illustrate how a circuit design made of just two Re-FeFETs exhibits high logic expressivity with reconfigurability at runtime to implement several key non-volatile 2-input logic functions. Moreover, the Re-FeFET circuit demonstrates remarkable compactness, with an up to 80% reduction in transistor count compared to standard CMOS design. The 2D van de Waals Re-FeFET devices therefore exhibit groundbreaking potential for both More-than-Moore and beyond-Moore future of electronics, in particular for an energy-efficient implementation of in-memory computing and machine learning hardware, due to their multifunctionality and design compactness.


On the absence of structure factors in concentrated colloidal suspensions and nanocomposites. (arXiv:2310.14682v1 [cond-mat.soft])
Anne-Caroline Genix (L2C), Julian Oberdisse (L2C)

Small-angle scattering is a commonly used tool to analyze the dispersion of nanoparticles in all kinds of matrices. Besides some obvious cases, the associated structure factor is often complex and cannot be reduced to a simple interparticle interaction, like excluded volume only. In recent experiments, we have encountered a surprising absence of structure factors (S(q) = 1) in scattering from rather concentrated polymer nanocomposites [A.-C. Genix et al, ACS Appl. Mater. Interfaces 11 (2019) 17863]. In this case, quite pure form factor scattering is observed. This somewhat ``ideal'' structure is further investigated here making use of reverse Monte Carlo simulations in order to shed light on the corresponding nanoparticle structure in space. By fixing the target ``experimental'' apparent structure factor to one over a given q-range in these simulations, we show that it is possible to find dispersions with this property. The influence of nanoparticle volume fraction and polydispersity has been investigated, and it was found that for high concentrations only a high polydispersity allows reaching a state of S = 1. The underlying structure in real space is discussed in terms of the pair-correlation function, which evidences the importance of attractive interactions between polydisperse nanoparticles. The calculation of partial structure factors shows that there is no specific ordering of large or small particles, but that the presence of attractive interactions together with polydispersity allows reaching an almost ``structureless'' state.


Complete zero-energy flat bands of surface states in fully gapped chiral noncentrosymmetric superconductors. (arXiv:2310.14800v1 [cond-mat.supr-con])
Clara J. Lapp, Julia M. Link, Carsten Timm

Noncentrosymmetric superconductors can support flat bands of zero-energy surface states in part of their surface Brillouin zone. This requires that they obey time-reversal symmetry and have a sufficiently strong triplet-to-singlet-pairing ratio to exhibit nodal lines in the bulk. These bands are protected by a winding number that relies on chiral symmetry, which is realized as the product of time-reversal and particle-hole symmetry. We reveal a way to stabilize a flat band in the entire surface Brillouin zone, while the bulk dispersion is fully gapped. This idea could lead to a robust platform for quantum computation and represents an alternative route to strongly correlated flat bands in two dimensions, besides twisted bilayer graphene. The necessary ingredient is an additional spin-rotation symmetry that forces the direction of the spin-orbit-coupling vector not to depend on the momentum component normal to the surface. We define a winding number which leads to flat zero-energy surface bands due to bulk-boundary correspondence. We discuss under which conditions this winding number is nonzero in the entire surface Brillouin zone and verify the occurrence of zero-energy surface states by exact numerical diagonalization of the Bogoliubov-de Gennes Hamiltonian for a slab. In addition, we consider how a weak breaking of the additional symmetry affects the surface band, employing first-order perturbation theory and a quasiclassical approximation. We find that the surface states and the bulk gap persist for weak breaking of the additional symmetry but that the band does not remain perfectly flat. The broadening of the band strongly depends on the deviation of the spin-orbit-coupling vector from its unperturbed direction as well as on the spin-orbit-coupling strength and the triplet-pairing amplitude.


pyCOFBuilder: A python package for automated assembly of Covalent Organic Framework structures. (arXiv:2310.14822v1 [cond-mat.mtrl-sci])
Felipe Lopes Oliveira, Pierre Mothé Esteves

Covalent Organic Frameworks (COFs) have gained significant popularity in recent years due to their unique ability to provide a high surface area and customizable pore geometry and chemistry. These traits make COFs a highly promising choice for a range of applications. However, with their vast potential structures, exploring COFs experimentally can be challenging and time-consuming, yet it remains an attractive avenue for computational high-throughput studies. However, generating COF structures can be a time-consuming and challenging task. To address this challenge, here we introduce the pyCOFBuilder, an open-source Python package designed to facilitate the generation of COF structures for computational studies. The pyCOFBuilder software provides an easy-to-use set of functionalities to generate COF structures following the reticular approach. In this paper, we describe the implementation, main features, and capabilities of the pyCOFBuilder demonstrating its utility for generating COF structures with varying topologies and chemical properties. pyCOFBuilder is freely available on GitHub at https://github.com/lipelopesoliveira/pyCOFBuilder.


Feature Spectrum Topology. (arXiv:2310.14832v1 [cond-mat.mtrl-sci])
Baokai Wang, Yi-Chun Hung, Xiaoting Zhou, Tzen Ong, Hsin Lin

Topology is a fundamental aspect of quantum physics, and it has led to key breakthroughs and results in various fields of quantum materials. In condensed matters, this has culminated in the recent discovery of symmetry-protected topological phases. However, symmetry-based topological characterizations rely heavily on symmetry analysis and are incapable of detecting the topological phases in systems where the symmetry is broken, thus missing a large portion of interesting topological physics. Here, we propose a new approach to understanding the topological nature of quantum materials, which we call feature spectrum topology. In this framework, the ground-state is separated into different partitions by the eigenspectrum of a feature, a particular chosen internal quantum degree of freedom, such as spin or pseudo-spin, and the topological properties are determined by analysis of these ground-state partitions. We show that bulk-boundary correspondence guarantees gapless spectral flows in either one of the energy or feature spectrum. Most importantly, such 'feature-energy duality' of gapless spectral flows serves as a fundamental manifestation of a topological phase, thereby paving a new way towards topological characterizations beyond symmetry considerations. Our development reveals the topological nature of a quantum ground state hidden outside symmetry-based characterizations, hence, providing a platform for a more refined search of unconventional topological materials.


Inheritance of the exciton geometric structure from Bloch electrons in two-dimensional layered semiconductors. (arXiv:2310.14856v1 [cond-mat.mes-hall])
Jianju Tang, Songlei Wang, Hongyi Yu

We theoretically studied the exciton geometric structure in layered semiconducting transition metal dichalcogenides. Using the well-developed three-orbital tight-binding models for the electron and hole constituents, an effective exciton Hamiltonian can be constructed and solved perturbatively. We show that the electron-hole Coulomb interaction gives rise to a non-trivial inheritance of the exciton geometric structure from Bloch electrons, which manifests as a center-of-mass anomalous Hall velocity of the exciton when two external fields are applied on the electron and hole constituents, respectively. The form of the center-of-mass anomalous velocity is obtained, which is found to exhibit a non-trivial dependence on the fields as well as the exciton wave function.


Effects of inorganic seed promoters on MoS2 few-layers grown via chemical vapor deposition. (arXiv:2310.14923v1 [cond-mat.mtrl-sci])
Alessandro Cataldo (1 2), Pinaka Pani Tummala (1 3 4), Christian Martella (1), Carlo Spartaco Casari (5), Alessandro Molle (1), Alessio Lamperti (1) ((1) CNR-IMM, Agrate Brianza Unit, via C. Olivetti 2, Agrate Brianza, I-20864, Italy (2) Dipartimento di Chimica, Materiali e Ingegneria Chimica, Politecnico di Milano, P.zza Leonardo da Vinci 32, edificio 6, I-20133 Milano, Italy (3) Department of Physics and Astronomy, University of Leuven, Celestijnenlaan 200D, B-3001 Leuven, Belgium (4) Interdisciplinary Laboratories for Advanced Materials Physics (I-LAMP), Dipartimento di Matematica e Fisica, Università Cattolica del Sacro Cuore, via della Garzetta 48, 25133 Brescia, Italy (5) Dipartimento di Energia, Politecnico di Milano, via Ponzio 34/3, I-20133 Milano, Italy)

In the last years, transition metal dichalcogenides (TMDs), especially at the two-dimensional (2D) limit, gained a large interest due to their unique optical and electronic properties. Among them, MoS2 received great attention from the scientific community due to its versatility, workability, and applicability in a large number of fields such as electronics, optoelectronics and electrocatalysis. To open the possibility of 2D-MoS2 exploitation, its synthesis over large macroscopic areas using cost-effective methods is fundamental. In this study, we report a method for the synthesis of large-area (~ cm2) few-layers MoS2 via liquid precursor CVD (L-CVD), where the Mo precursor (i.e. ammonium heptamolybdate AHM) is provided via a solution that is spin-coated over the substrate. Given the capability of organic and inorganic molecules, such as alkaline salts, to enhance MoS2 growth, we investigated the action of different inorganic salts as seed promoters. In particular, by using visible Raman spectroscopy, we focused on the effect of Na(OH), KCl, KI, and Li(OH) on the thickness, morphology, uniformity and degree of coverage of the grown MoS2. We optimized the process tuning parameters such as the volume of spin-coated solution, the growth temperature, and the seed promoter concentration, to synthesise the lowest possible thickness which resulted to be 2 layers (2L) of the highest quality. We witnessed that the addition of an inorganic seed promoter in the solution improves the extension of the grown MoS2 promoting lateral growth front, and therefore the degree of coverage. From this study, we conclude that, amongst the investigated seed promoters, K-based salts proved to grant the growth of high-quality two-layer MoS2 with optimal and uniform coverage of the SiO2/Si substrate surface.


Robustness of stress focusing in soft lattices under topology-switching deformation. (arXiv:2310.14972v1 [cond-mat.soft])
Caleb Widstrand, Xiaoming Mao, Stefano Gonella

Recent developments in topological mechanics have demonstrated the ability of Maxwell lattices to effectively focus stress along domain walls between differently polarized domains. The focusing ability can be exploited to protect the lattice bulk from accidental stress concentration -- and eventually onset and propagation of fracture -- at structural hot spots such as defects and cracks. A recent study has revisited the problem for structural lattices featuring non-ideal hinges, showing that the focusing remains robust, albeit diluted in strength. Realizing that the problem of domain wall localization has been traditionally framed in the context of linear elasticity, in this work we extend the study to the realm of soft structures undergoing nonlinear finite deformation. Through experiments performed on silicone hyperelastic prototypes, we assess and quantify the robustness of the phenomenon against the macroscopic shape changes induced by large deformation, with special attention to deformation levels that alter the topology of the bulk, lifting the topological protection. Furthermore, we identify a simple geometric indicator for this transition.


Experimental signatures of quantum and topological states in frustrated magnetism. (arXiv:2310.15071v1 [cond-mat.str-el])
J. Khatua, B. Sana, A. Zorko, M. Gomilsek, K. Sethupathi M. S. Ramachandra Rao, M. Baenitz, B. Schmidt, P. Khuntia

Frustration in magnetic materials arising from competing exchange interactions can prevent the system from adopting long-range magnetic order and can instead lead to a diverse range of novel quantum and topological states with exotic quasiparticle excitations. Here, we review prominent examples of such emergent phenomena, including magnetically-disordered and extensively degenerate spin ices, which feature emergent magnetic monopole excitations, highly-entangled quantum spin liquids with fractional spinon excitations, topological order and emergent gauge fields, as well as complex particle-like topological spin textures known as skyrmions. We provide an overview of recent advances in the search for magnetically-disordered candidate materials on the three-dimensional pyrochlore lattice and two-dimensional triangular, kagome and honeycomb lattices, the latter with bond-dependent Kitaev interactions, and on lattices supporting topological magnetism. We highlight experimental signatures of these often elusive phenomena and single out the most suitable experimental techniques that can be used to detect them. Our review also aims at providing a comprehensive guide for designing and investigating novel frustrated magnetic materials, with the potential of addressing some important open questions in contemporary condensed matter physics.


Emulating moir\'e materials with quasiperiodic circuit quantum electrodynamics. (arXiv:2310.15103v1 [cond-mat.mes-hall])
Tobias Herrig, Christina Koliofoti, Jedediah H. Pixley, Elio J. König, Roman-Pascal Riwar

Topological bandstructures interfering with moir\'e superstructures give rise to a plethora of emergent phenomena, which are pivotal for correlated insulating and superconducting states of twisttronics materials. While quasiperiodicity was up to now a notion mostly reserved for solid-state materials and cold atoms, we here demonstrate the capacity of conventional superconducting circuits to emulate moir\'e physics in charge space. With two examples, we show that Hofstadter's butterfly and the magic-angle effect, are directly visible in spectroscopic transport measurements. Importantly, these features survive in the presence of harmonic trapping potentials due to parasitic linear capacitances. Our proposed platform benefits from unprecedented tuning capabilities, and opens the door to probe incommensurate physics in virtually any spatial dimension.


Dynamics of a trapped Fermi gas in the BCS phase. (arXiv:cond-mat/0509373v3 [cond-mat.other] UPDATED)
M. Urban, P. Schuck

We derive semiclassical transport equations for a trapped atomic Fermi gas in the BCS phase at temperatures between zero and the superfluid transition temperature. These equations interpolate between the two well-known limiting cases of superfluid hydrodynamics at zero temperature and the Vlasov equation at the critical one. The linearized version of these equations, valid for small deviations from equilibrium, is worked out and applied to two simple examples where analytical solutions can be found: a sound wave in a uniform medium and the quadrupole excitation in a spherical harmonic trap. In spite of some simplifying approximations, the main qualitative results of quantum mechanical calculations are reproduced, which are the different frequencies of the quadrupole mode at zero and the critical temperature and strong Landau damping at intermediate temperatures. In addition we suggest a numerical method for solving the semiclassical equations without further approximations.


Tunable spin and valley excitations of correlated insulators in $\Gamma$-valley moir\'e bands. (arXiv:2206.10631v3 [cond-mat.mes-hall] UPDATED)
Benjamin A. Foutty, Jiachen Yu, Trithep Devakul, Carlos R. Kometter, Yang Zhang, Kenji Watanabe, Takashi Taniguchi, Liang Fu, Benjamin E. Feldman

Moir\'e superlattices formed from transition metal dichalcogenides (TMDs) have been shown to support a variety of quantum electronic phases that are highly tunable using applied electromagnetic fields. While the valley character of the low-energy states dramatically affects optoelectronic properties in the constituent TMDs, this degree of freedom has yet to be fully explored in moir\'e systems. Here, we establish twisted double bilayer WSe$_2$ as an experimental platform to study electronic correlations within $\Gamma$-valley moir\'e bands. Through a combination of local and global electronic compressibility measurements, we identify charge-ordered phases at multiple integer and fractional moir\'e band fillings $\nu$. By measuring the magnetic field dependence of their energy gaps and the chemical potential upon doping, we reveal spin-polarized ground states with novel spin polaron quasiparticle excitations. In addition, an applied displacement field allows us to realize a new mechanism of metal-insulator transition at $\nu = -1$ driven by tuning between $\Gamma$- and $K$-valley moir\'e bands. Together, our results demonstrate control over both the spin and valley character of the correlated ground and excited states in this system.


4Ward: a Relayering Strategy for Efficient Training of Arbitrarily Complex Directed Acyclic Graphs. (arXiv:2209.02037v2 [cs.NE] UPDATED)
Tommaso Boccato, Matteo Ferrante, Andrea Duggento, Nicola Toschi

Thanks to their ease of implementation, multilayer perceptrons (MLPs) have become ubiquitous in deep learning applications. The graph underlying an MLP is indeed multipartite, i.e. each layer of neurons only connects to neurons belonging to the adjacent layer. In contrast, in vivo brain connectomes at the level of individual synapses suggest that biological neuronal networks are characterized by scale-free degree distributions or exponentially truncated power law strength distributions, hinting at potentially novel avenues for the exploitation of evolution-derived neuronal networks. In this paper, we present ``4Ward'', a method and Python library capable of generating flexible and efficient neural networks (NNs) from arbitrarily complex directed acyclic graphs. 4Ward is inspired by layering algorithms drawn from the graph drawing discipline to implement efficient forward passes, and provides significant time gains in computational experiments with various Erd\H{o}s-R\'enyi graphs. 4Ward not only overcomes the sequential nature of the learning matrix method, by parallelizing the computation of activations, but also addresses the scalability issues encountered in the current state-of-the-art and provides the designer with freedom to customize weight initialization and activation functions. Our algorithm can be of aid for any investigator seeking to exploit complex topologies in a NN design framework at the microscale.


Symmetry TFTs for Non-Invertible Defects. (arXiv:2209.11062v3 [hep-th] UPDATED)
Justin Kaidi, Kantaro Ohmori, Yunqin Zheng

Given any symmetry acting on a $d$-dimensional quantum field theory, there is an associated $(d+1)$-dimensional topological field theory known as the Symmetry TFT (SymTFT). The SymTFT is useful for decoupling the universal quantities of quantum field theories, such as their generalized global symmetries and 't Hooft anomalies, from their dynamics. In this work, we explore the SymTFT for theories with Kramers-Wannier-like duality symmetry in both $(1+1)$d and $(3+1)$d quantum field theories. After constructing the SymTFT, we use it to reproduce the non-invertible fusion rules of duality defects, and along the way we generalize the concept of duality defects to \textit{higher} duality defects. We also apply the SymTFT to the problem of distinguishing intrinsically versus non-intrinsically non-invertible duality defects in $(1+1)$d.


Phase transitions in 3-dimensional Dirac semi-metals using Schwinger-Dyson equations. (arXiv:2210.08563v2 [cond-mat.str-el] UPDATED)
Margaret E. Carrington, Wade N. Cowie, Brett A. Meggison

We study the semi-metal/insulator quantum phase transition in three-dimensional Dirac semi-metals by solving a set of Schwinger-Dyson equations. We study the effect of an anisotropic fermion velocity on the critical coupling of the transition. We consider the influence of several different approximations that are commonly used in the literature and show that results for the critical coupling change considerably when some of these approximations are relaxed. Most importantly, the nature of the dependence of the critical coupling on the anisotropy depends strongly on the approximations that are used for the photon polarization tensor. On the one hand, this means that calculations that include full photon dynamics are necessary to answer even the basic question of whether the critical coupling increases or decreases with anisotropy. On the other hand, our results mean that it is possible that anisotropy could provide a mechanism to promote dynamical gap generation in realistic three-dimensional Dirac semi-metallic materials.


Edge channels in a graphene Fabry-Perot interferometer. (arXiv:2210.15036v3 [cond-mat.mes-hall] UPDATED)
S. Ihnatsenka

Quantum-mechanical calculations of electron magnetotransport in graphene Fabry-P\'{e}rot interferometers are presented with a focus on the role of spatial structure of edge channels. For an interferometer that is made by removing carbon atoms, which is typically realized in nanolithography experiments, the constrictions are shown to cause strong inter-channel scattering that establishes local equilibrium and makes the electron transport non-adiabatic. Nevertheless, two-terminal conductance reveals a common Aharonov-Bohm oscillation pattern, independent of crystallographic orientation, which is accompanied by single-particle states that sweep through the Fermi energy for the edge channels circulating along the physical boundary of the device. The interferometer constrictions host the localized states that might shorten the device or disrupt the oscillation pattern. For an interferometer that is created by electrostatic confinement, which is typically done in the split-gate experiments, electron transport is shown to be adiabatic if the staggered potential is introduced additionally into the model. Interference visibility decays exponentially with temperature with a weaker dependence at low temperature.


Exploring the Elastic Properties and Fracture Patterns of Me-Graphene Monolayers and Nanotubes through Reactive Molecular Dynamics Simulations. (arXiv:2303.07518v2 [cond-mat.mtrl-sci] UPDATED)
Marcelo L. Pereira Junior, José. M. De Sousa, Wjefferson H. S. Brandão, Douglas. S. Galvão, Alexandre F. Fonseca, Luiz A. Ribeiro Junior

Me-graphene (MeG) is a novel two-dimensional (2D) carbon allotrope. Due to its attractive electronic and structural properties, it is important to study the mechanical behavior of MeG in its monolayer and nanotube topologies. In this work, we conducted fully atomistic reactive molecular dynamics simulations using the Tersoff force field to investigate their mechanical properties and fracture patterns. Our results indicate that Young's modulus of MeG monolayers is about 414 GPa and in the range of 421-483 GPa for the nanotubes investigated here. MeG monolayers and MeGNTs directly undergo from elastic to complete fracture under critical strain without a plastic regime.


Flat bands and multi-state memory devices from chiral domain wall superlattices in magnetic Weyl semimetals. (arXiv:2303.16918v3 [cond-mat.mes-hall] UPDATED)
Vivian Rogers, Swati Chaudhary, Richard Nguyen, Jean Anne Incorvia

We propose a novel analog memory device utilizing the gigantic magnetic Weyl semimetal (MWSM) domain wall (DW) magnetoresistance. We predict that the nucleation of domain walls between contacts will strongly modulate the conductance and allow for multiple memory states, which has been long sought-after for use in magnetic random access memories or memristive neuromorphic computing platforms. We motivate this conductance modulation by analyzing the electronic structure of the helically-magnetized MWSM Hamiltonian, and report tunable flat bands in the direction of transport in a helically-magnetized region of the sample for Bloch and Neel-type domain walls via the onset of a local axial Landau level spectrum within the bulk of the superlattice. We show that Bloch devices also provide means for the generation of chirality-polarized currents, which provides a path towards nanoelectronic utilization of chirality as a new degree of freedom in spintronics.


Complete crystalline topological invariants from partial rotations in (2+1)D invertible fermionic states and Hofstadter's butterfly. (arXiv:2303.16919v2 [cond-mat.str-el] UPDATED)
Yuxuan Zhang, Naren Manjunath, Ryohei Kobayashi, Maissam Barkeshli

The theory of topological phases of matter predicts invariants protected only by crystalline symmetry, yet it has been unclear how to extract these from microscopic calculations in general. Here we show how to extract a set of many-body invariants $\{\Theta_{\text{o}}^{\pm}\}$, where ${\text{o}}$ is a high symmetry point, from partial rotations in (2+1)D invertible fermionic states. Our results apply in the presence of magnetic field and Chern number $C \neq 0$, in contrast to previous work. $\{\Theta_{\text{o}}^{\pm}\}$ together with $C$, chiral central charge $c_-$, and filling $\nu$ provide a complete many-body characterization of the topological state with symmetry group $G = \text{U}(1) \times_\phi [\mathbb{Z}^2 \rtimes \mathbb{Z}_M]$. Moreover, all these many-body invariants can be obtained from a single bulk ground state, without inserting additional defects. We perform numerical computations on the square lattice Hofstadter model. Remarkably, these match calculations from conformal and topological field theory, where $G$-crossed modular $S, T$ matrices of symmetry defects play a crucial role. Our results provide additional colorings of Hofstadter's butterfly, extending recently discovered colorings by the discrete shift and quantized charge polarization.


Beyond Multilayer Perceptrons: Investigating Complex Topologies in Neural Networks. (arXiv:2303.17925v2 [cs.NE] UPDATED)
Tommaso Boccato, Matteo Ferrante, Andrea Duggento, Nicola Toschi

In this study, we explore the impact of network topology on the approximation capabilities of artificial neural networks (ANNs), with a particular focus on complex topologies. We propose a novel methodology for constructing complex ANNs based on various topologies, including Barab\'asi-Albert, Erd\H{o}s-R\'enyi, Watts-Strogatz, and multilayer perceptrons (MLPs). The constructed networks are evaluated on synthetic datasets generated from manifold learning generators, with varying levels of task difficulty and noise, and on real-world datasets from the UCI suite. Our findings reveal that complex topologies lead to superior performance in high-difficulty regimes compared to traditional MLPs. This performance advantage is attributed to the ability of complex networks to exploit the compositionality of the underlying target function. However, this benefit comes at the cost of increased forward-pass computation time and reduced robustness to graph damage. Additionally, we investigate the relationship between various topological attributes and model performance. Our analysis shows that no single attribute can account for the observed performance differences, suggesting that the influence of network topology on approximation capabilities may be more intricate than a simple correlation with individual topological attributes. Our study sheds light on the potential of complex topologies for enhancing the performance of ANNs and provides a foundation for future research exploring the interplay between multiple topological attributes and their impact on model performance.


Grand-canonical Thermodynamic Formalism via IFS: volume, temperature, gas pressure and grand-canonical topological pressure. (arXiv:2305.01590v3 [math.DS] UPDATED)
A. O. Lopes, E. R. Oliveira, W. de S. Pedra, V. Vargas

We consider here a dynamic model for a gas in which a variable number of particles $N \in \mathbb{N}_0 := \mathbb{N} \cup \{0\}$ can be located at a site. This point of view leads us to the grand-canonical framework and the need for a chemical potential. The dynamics is played by the shift acting on the set of sequences $\Omega := \mathcal{A}^\mathbb{N}$, where the alphabet is $\mathcal{A} := \{1,2,...,r\}$. Introducing new variables like the number of particles $N$ and the chemical potential $\mu$, we adapt the concept of grand-canonical partition sum of thermodynamics of gases to a symbolic dynamical setting considering a Lipschitz family of potentials $% (A_N)_{N \in \mathbb{N}_0}$, $A_N:\Omega \to \mathbb{R}$. Our main results will be obtained from adapting well-known properties of the Thermodynamic Formalism for IFS with weights to our setting. In this direction, we introduce the grand-canonical-Ruelle operator: $\mathcal{L}_{\beta, \mu}(f)=g$, when, $\beta>0,\mu<0,$ and

\medskip $\,\,\,\,\,\,\,\,\,\,\,\,\,\,g(x)= \mathcal{L}_{\beta, \mu}(f) (x) =\sum_{N \in \mathbb{N}_0} e^{\beta \, \mu\, N }\, \sum_{j \in \mathcal{A}} e^{- \,\beta\, A_N(jx)} f(jx). $ \medskip

We show the existence of the main eigenvalue, an associated eigenfunction, and an eigenprobability for $\mathcal{L}_{\beta, \mu}^*$. We can show the analytic dependence of the eigenvalue on the grand-canonical potential. Considering the concept of entropy for holonomic probabilities on $\Omega\times \mathcal{A}^{\mathbb{N}_0}$, we relate these items with the variational problem of maximizing grand-canonical pressure. In another direction, in the appendix, we briefly digress on a possible interpretation of the concept of topological pressure as related to the gas pressure of gas thermodynamics.


From Ergodicity to Many-Body Localization in a One-Dimensional Interacting Non-Hermitian Stark System. (arXiv:2305.13636v2 [cond-mat.dis-nn] UPDATED)
Jinghu Liu, Zhihao Xu

Recent studies on disorder-induced many-body localization (MBL) in non-Hermitian quantum systems have attracted great interest. However, the non-Hermitian disorder-free MBL still needs to be clarified. We consider a one-dimensional interacting Stark model with nonreciprocal hoppings having time-reversal symmetry, the properties of which are boundary dependent. Under periodic boundary conditions (PBCs), such a model exhibits three types of phase transitions: the real-complex transition of eigenenergies, the topological phase transition, and the non-Hermitian Stark MBL transition. The real-complex and topological phase transitions occur at the same point in the thermodynamic limit, but do not coincide with the non-Hermitian Stark MBL transition, which is quite different from the non-Hermitian disordered cases. By the level statistics, the system undergoes from the Ginibre ensemble (GE) to Gaussian orthogonal ensemble (GOE) to Possion ensemble (PE) transitions with the increase of the linear tilt potential's strength $\gamma$. The real-complex transition of the eigenvalues is accompanied by the GE-to-GOE transition in the ergodic regime. Moreover, the second transition of the level statistics corresponds to the occurrence of non-Hermitian Stark MBL. We demonstrate that the non-Hermitian Stark MBL is robust and shares many similarities with disorder-induced MBL, which several existing characteristic quantities of the spectral statistics and eigenstate properties can confirm. The dynamical evolutions of the entanglement entropy and the density imbalance can distinguish the real-complex and Stark MBL transitions. Finally, we find that our system under open boundary conditions lacks a real-complex transition, and the transition of non-Hermitian Stark MBL is the same as that under PBCs.


Ground state stability, symmetry, and degeneracy in Mott insulators with long range interactions. (arXiv:2306.00221v2 [cond-mat.str-el] UPDATED)
Dmitry Manning-Coe, Barry Bradlyn

Recently, models with long-range interactions -- known as Hatsugai-Kohmoto (HK) models -- have emerged as a promising tool to study the emergence of superconductivity and topology in strongly correlated systems. Two obstacles, however, have made it difficult to understand the applicability of these models, especially to topological features: they have thermodynamically large ground state degeneracies, and they tacitly assume spin conservation. We show that neither are essential to HK models and that both can be avoided by introducing interactions between tight-binding states in the orbital basis, rather than between energy eigenstates. To solve these "orbital" models, we introduce a general technique for solving HK models and show that previous models appear as special cases. We illustrate our method by exactly solving graphene and the Kane-Mele model with HK interactions. Both realize Mott insulating phases with finite magnetic susceptibility; the graphene model has a fourfold degenerate ground state while the Kane-Mele model has a nondegenerate ground state in the presence of interactions. Our technique then allows us to study the effect of strong interactions on symmetry-enforced degeneracy in spin-orbit coupled double-Dirac semimetals. We show that adding HK interactions to a double Dirac semi-metal leads to a Mott insulating, spin liquid phase. We then use a Schrieffer-Wolff transformation to express the low-energy Hamiltonian in terms of the spin degrees of freedom, making the spin-charge separation explicit. Finally, we enumerate a broader class of symmetry-preserving HK interactions and show how they can violate insulating filling constraints derived from space group symmetries. This suggests that new approaches are needed to study topological order in the presence of long-range interactions of the HK type.


Universal defect density scaling in an oscillating dynamic phase transition. (arXiv:2306.03803v2 [cond-mat.stat-mech] UPDATED)
Wei-can Yang, Makoto Tsubota, Adolfo del Campo, Hua-Bi Zeng

Universal scaling laws govern the density of topological defects generated while crossing an equilibrium continuous phase transition. The Kibble-Zurek mechanism (KZM) predicts the dependence on the quench time for slow quenches. By contrast, for fast quenches, the defect density scales universally with the amplitude of the quench. We show that universal scaling laws apply to dynamic phase transitions driven by an oscillating external field. The difference in the energy response of the system to a periodic potential field leads to energy absorption, spontaneous breaking of symmetry, and its restoration. We verify the associated universal scaling laws, providing evidence that the critical behavior of non-equilibrium phase transitions can be described by time-average critical exponents combined with the KZM. Our results demonstrate that the universality of critical dynamics extends beyond equilibrium criticality, facilitating the understanding of complex non-equilibrium systems.


Engineering phase and density of Bose-Einstein condensates in curved waveguides with toroidal topology. (arXiv:2306.11873v4 [cond-mat.quant-gas] UPDATED)
Yelyzaveta Nikolaieva, Luca Salasnich, Alexander Yakimenko

We investigate the effects of ellipticity-induced curvature on atomic Bose-Einstein condensates confined in quasi-one-dimensional closed-loop waveguides. Our theoretical study reveals intriguing phenomena arising from the interplay between curvature and interactions. Density modulations are observed in regions of high curvature, but these modulations are suppressed by strong repulsive interactions. Additionally, we observe phase accumulation in regions with the lowest curvature when the waveguide with persistent current is squeezed. Furthermore, waveguides hosting persistent currents exhibit dynamic transformations between states with different angular momenta. These findings provide insights into the behavior of atomic condensates in curved waveguides, with implications for fundamental physics and quantum technologies. The interplay between curvature and interactions offers opportunities for exploring novel quantum phenomena and engineering quantum states in confined geometries.


Light-Driven Nanoscale Vectorial Currents. (arXiv:2307.11928v2 [cond-mat.mes-hall] UPDATED)
Jacob Pettine, Prashant Padmanabhan, Teng Shi, Lauren Gingras, Luke McClintock, Chun-Chieh Chang, Kevin W. C. Kwock, Long Yuan, Yue Huang, John Nogan, Jon K. Baldwin, Peter Adel, Ronald Holzwarth, Abul K. Azad, Filip Ronning, Antoinette J. Taylor, Rohit P. Prasankumar, Shi-Zeng Lin, Hou-Tong Chen

Controlled charge flows are fundamental to many areas of science and technology, serving as carriers of energy and information, as probes of material properties and dynamics, and as a means of revealing or even inducing broken symmetries. Emerging methods for light-based current control offer promising routes beyond the speed and adaptability limitations of conventional voltage-driven systems. However, optical generation and manipulation of currents at nanometer spatial scales remains a basic challenge and a crucial step towards scalable optoelectronic systems for microelectronics and information science. Here, we introduce vectorial optoelectronic metasurfaces in which ultrafast light pulses induce local directional charge flows around symmetry-broken plasmonic nanostructures, with tunable responses and arbitrary patterning down to sub-diffractive nanometer scales. Local symmetries and vectorial current distributions are revealed by polarization- and wavelength-sensitive electrical readout and terahertz (THz) emission, while spatially-tailored global currents are demonstrated in the direct generation of elusive broadband THz vector beams. We show that in graphene, a detailed interplay between electrodynamic, thermodynamic, and hydrodynamic degrees of freedom gives rise to rapidly-evolving nanoscale driving forces and charge flows under extreme temporal and spatial confinement. These results set the stage for versatile patterning and optical control over nanoscale currents in materials diagnostics, THz spectroscopies, nano-magnetism, and ultrafast information processing.


Minimal model for the flat bands in copper-substituted lead phosphate apatite: Strong diamagnetism from multi-orbital physics. (arXiv:2308.01315v3 [cond-mat.supr-con] UPDATED)
Omid Tavakol, Thomas Scaffidi

The claims that a copper-substituted lead apatite, denoted as CuPb$_9$(PO$_4$)$_6$OH$_2$, could be a room-temperature superconductor have led to an intense research activity. While other research groups did not confirm these claims, and the hope of realizing superconductivity in this compound has all but vanished, other findings have emerged which motivate further work on this material. In fact, Density Functional Theory (DFT) calculations indicate the presence of two nearly flat bands near the Fermi level, which are known to host strongly correlated physics. In order to facilitate the theoretical study of the intriguing physics associated with these two flat bands, we propose a minimal tight-binding model which reproduces their main features. We then calculate the orbital magnetic susceptibility of our two-band model and find a large diamagnetic response which arises due to the multi-orbital nature of the bands and which could provide an explanation for the strong diamagnetism reported in experiments.


Topological Floquet Flat Bands in Irradiated Alternating Twist Multilayer Graphene. (arXiv:2309.11685v2 [cond-mat.mes-hall] UPDATED)
Yingyi Huang

We study the appearance of topological Floquet flat bands in alternating-twist multilayer graphene, which has alternating relative twist angle $\pm\theta$ near the first magic angle. While the system hosts both flat bands and a steep Dirac cone in the static case, the circularly polarized laser beam can open a gap at the Moir\'{e} $K$ point and create Floquet flat bands carrying nonzero Chern numbers. Considering recent lattice-relaxation results, we find that the topological flat band is well-isolated for the effective interlayer tunneling in $n=3, 4, 5$ layers. Such dynamically produced topological flat bands are potentially observed in the experiment and thus provide a feasible way to realize the fractional Chern insulator.


Gapped Phases with Non-Invertible Symmetries: (1+1)d. (arXiv:2310.03784v2 [hep-th] UPDATED)
Lakshya Bhardwaj, Lea E. Bottini, Daniel Pajer, Sakura Schafer-Nameki

We propose a general framework to characterize gapped infra-red (IR) phases of theories with non-invertible (or categorical) symmetries. In this paper we focus on (1+1)d gapped phases with fusion category symmetries. The approach that we propose uses the Symmetry Topological Field Theory (SymTFT) as a key input: associated to a field theory in d spacetime dimensions, the SymTFT lives in one dimension higher and admits a gapped boundary, which realizes the categorical symmetries. It also admits a second, physical, boundary, which is generically not gapped. Upon interval compactification of the SymTFT by colliding the gapped and physical boundaries, we regain the original theory. In this paper, we realize gapped symmetric phases by choosing the physical boundary to be a gapped boundary condition as well. This set-up provides computational power to determine the number of vacua, the symmetry breaking pattern, and the action of the symmetry on the vacua. The SymTFT also manifestly encodes the order parameters for these gapped phases, thus providing a generalized, categorical Landau paradigm for (1+1)d gapped phases. We find that for non-invertible symmetries the order parameters involve multiplets containing both untwisted and twisted sector local operators, and hence can be interpreted as mixtures of conventional and string order parameters. We also observe that spontaneous breaking of non-invertible symmetries can lead to vacua that are physically distinguishable: unlike the standard symmetries described by groups, non-invertible symmetries can have different actions on different vacua of an irreducible gapped phase. This leads to the presence of relative Euler terms between physically distinct vacua. We also provide a mathematical description of symmetric gapped phases as 2-functors from delooping of fusion category characterizing the symmetry to Euler completion of 2-vector spaces.


Categorical Landau Paradigm for Gapped Phases. (arXiv:2310.03786v2 [cond-mat.str-el] UPDATED)
Lakshya Bhardwaj, Lea E. Bottini, Daniel Pajer, Sakura Schafer-Nameki

We propose a unified framework to classify gapped infra-red (IR) phases with categorical symmetries, leading to a generalized, categorical Landau paradigm. This is applicable in any dimension and gives a succinct, comprehensive, and computationally powerful approach to classifying gapped symmetric phases. The key tool is the symmetry topological field theory (SymTFT), which is a one dimension higher TFT with two boundaries, which we choose both to be topological. We illustrate the general idea for (1+1)d gapped phases with categorical symmetries and suggest higher-dimensional extensions.


Turning non-magnetic two-dimensional molybdenum disulfide into room temperature magnets by the synergistic effect of strain engineering and charge injection. (arXiv:2310.03995v2 [cond-mat.mtrl-sci] UPDATED)
Jing Wu, Ruyi Guo, Daoxiong Wu, Xiuling Li, Xiaojun Wu

The development of two-dimensional (2D) room temperature magnets is of great significance to the practical application of spintronic devices. However, the number of synthesized intrinsic 2D magnets is limited and the performances of them are not satisfactory, e.g. typically with low Curie temperature and poor environmental stability. Magnetic modulation based on developed 2D materials, especially non-magnetic 2D materials, can bring us new breakthroughs. Herein, we report room temperature ferromagnetism in halogenated MoS2 monolayer under the synergistic effect of strain engineering and charge injection, and the combined implementation of these two processes is based on the halogenation of MoS2. The adsorbed halogen atoms X (X = F, Cl, and Br) on the surface leads to lattice superstretching and hole injection, resulting in MoS2 monolayer exhibiting half-metallic properties, with one spin channel being gapless in the band structure. The Curie temperature of halogenated MoS2 monolayer is 513~615 K, which is much higher than the room temperature. In addition, large magnetic anisotropy energy and good environmental stability make halogenated MoS2 display great advantages in practical spintronic nanodevices.


Superfluidity meets the solid-state: frictionless mass-transport through a (5,5) carbon-nanotube. (arXiv:2310.07476v2 [cond-mat.mtrl-sci] UPDATED)
Alberto Ambrosetti, Pier Luigi Silvestrelli, Luca Salasnich

Superfluidity is a well-characterized quantum phenomenon which entails frictionless-motion of mesoscopic particles through a superfluid, such as $^4$He or dilute atomic-gases at very low temperatures. As shown by Landau, the incompatibility between energy- and momentum-conservation, which ultimately stems from the spectrum of the elementary excitations of the superfluid, forbids quantum-scattering between the superfluid and the moving mesoscopic particle, below a critical speed-threshold. Here we predict that frictionless-motion can also occur in the absence of a standard superfluid, i.e. when a He atom travels through a narrow (5,5) carbon-nanotube (CNT). Due to the quasi-linear dispersion of the plasmon and phonon modes that could interact with He, the (5,5) CNT embodies a solid-state analog of the superfluid, thereby enabling straightforward transfer of Landau's criterion of superfluidity. As a result, Landau's equations acquire broader generality, and may be applicable to other nanoscale friction phenomena, whose description has been so far purely classical.


Generation of isolated flat bands with tunable numbers through Moir\'e engineering. (arXiv:2310.07647v2 [cond-mat.mes-hall] UPDATED)
Xiaoting Zhou, Yi-Chun Hung, Baokai Wang, Arun Bansil

Unlike the spin-1/2 fermions, the Lieb and Dice lattices both host triply-degenerate low-energy excitations. Here, we discuss Moir\'e structures involving twisted bilayers of these lattices, which are shown to exhibit a tunable number of isolated flat bands near the Fermi level. These flat bands remain isolated from the high-energy bands even in the presence of small higher-order terms and chiral-symmetry-breaking interlayer tunneling. At small twist angles, thousands of flat bands can be generated to substantially amplify flat band physics. We demonstrate that these flat bands carry substantial quantum weight so that upon adding a BCS-type pairing potential, the associated superfluid weight would also be large, and the critical superconducting temperature would be tunable. Our study suggests a new pathway for flat-band engineering based on twisted bilayer Lieb and Dice lattices.


Mutual information and correlations across topological phase transitions in topologically ordered graphene zigzag nanoribbons. (arXiv:2310.08970v2 [cond-mat.mes-hall] UPDATED)
In-Hwan Lee, Hoang-Anh Le, S.-R. Eric Yang

Graphene zigzag nanoribbons, initially in a topologically ordered state, undergo a topological phase transition into crossover phases distinguished by quasi-topological order. We computed mutual information for both the topologically ordered phase and its crossover phases, revealing the following results: (i) In the topologically ordered phase, A-chirality carbon lines strongly entangle with B-chirality carbon lines on the opposite side of the zigzag ribbon. This entanglement persists but weakens in crossover phases. (ii) The upper zigzag edge entangles with non-edge lines of different chirality on the opposite side of the ribbon. (iii) Entanglement increases as more carbon lines are grouped together, regardless of the lines' chirality. No long-range entanglement was found in the symmetry-protected phase in the absence of disorder.


Tunneling density of states of fractional quantum Hall edges: an unconventional bosonization approach. (arXiv:2310.10319v3 [cond-mat.mes-hall] UPDATED)
Nikhil Danny Babu, Girish S. Setlur

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


Entanglement-Embedded Recurrent Network Architecture: Tensorized Latent State Propagation and Chaos Forecasting. (arXiv:2006.14698v1 [math.NA] CROSS LISTED)
Xiangyi Meng (Boston University), Tong Yang (Boston College)

Chaotic time series forecasting has been far less understood despite its tremendous potential in theory and real-world applications. Traditional statistical/ML methods are inefficient to capture chaos in nonlinear dynamical systems, especially when the time difference $\Delta t$ between consecutive steps is so large that a trivial, ergodic local minimum would most likely be reached instead. Here, we introduce a new long-short-term-memory (LSTM)-based recurrent architecture by tensorizing the cell-state-to-state propagation therein, keeping the long-term memory feature of LSTM while simultaneously enhancing the learning of short-term nonlinear complexity. We stress that the global minima of chaos can be most efficiently reached by tensorization where all nonlinear terms, up to some polynomial order, are treated explicitly and weighted equally. The efficiency and generality of our architecture are systematically tested and confirmed by theoretical analysis and experimental results. In our design, we have explicitly used two different many-body entanglement structures---matrix product states (MPS) and the multiscale entanglement renormalization ansatz (MERA)---as physics-inspired tensor decomposition techniques, from which we find that MERA generally performs better than MPS, hence conjecturing that the learnability of chaos is determined not only by the number of free parameters but also the tensor complexity---recognized as how entanglement entropy scales with varying matricization of the tensor.


Found 12 papers in prb
Date of feed: Tue, 24 Oct 2023 03:17:01 GMT

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Cladded phononic nodal frame state in biatomic alkali-metal sulfides
Tie Yang, Yang Gao, Liyu Hao, Haopeng Zhang, Xingwen Tan, Peng Wang, Zhenxiang Cheng, and Weikang Wu
Author(s): Tie Yang, Yang Gao, Liyu Hao, Haopeng Zhang, Xingwen Tan, Peng Wang, Zhenxiang Cheng, and Weikang Wu

With rapid progress, the current study of topological properties in condensed matter systems has been further extended from the electronic scope to the phononic perspective. Based on first-principles calculations, we present a systematic investigation on topological phononic states in a series of bi…


[Phys. Rev. B 108, 134310] Published Mon Oct 23, 2023

Current-driven motion of magnetic topological defects in ferromagnetic superconductors
Se Kwon Kim and Suk Bum Chung
Author(s): Se Kwon Kim and Suk Bum Chung

Recent years have seen a number of instances where magnetism and superconductivity intrinsically coexist. Our focus is on the case where spin-triplet superconductivity arises out of ferromagnetism, and we make a hydrodynamic analysis of the effect of a charge supercurrent on magnetic topological def…


[Phys. Rev. B 108, 134509] Published Mon Oct 23, 2023

Topological superconductivity from first principles. I. Shiba band structure and topological edge states of artificial spin chains
Bendegúz Nyári, András Lászlóffy, Gábor Csire, László Szunyogh, and Balázs Újfalussy
Author(s): Bendegúz Nyári, András Lászlóffy, Gábor Csire, László Szunyogh, and Balázs Újfalussy

Magnetic chains on superconductors hosting Majorana zero modes (MZMs) have attracted a great deal of interest due to their possible applications in fault-tolerant quantum computing. However, this is hindered by the lack of a detailed, quantitative understanding of these systems. As a significant ste…


[Phys. Rev. B 108, 134512] Published Mon Oct 23, 2023

Topological superconductivity from first principles. II. Effects from manipulation of spin spirals: Topological fragmentation, braiding, and quasi-Majorana bound states
András Lászlóffy, Bendegúz Nyári, Gábor Csire, László Szunyogh, and Balázs Újfalussy
Author(s): András Lászlóffy, Bendegúz Nyári, Gábor Csire, László Szunyogh, and Balázs Újfalussy

Recent advances in electron spin resonance techniques have allowed the manipulation of the spin of individual atoms, making magnetic atomic chains on superconducting hosts one of the most promising platform where topological superconductivity can be engineered. Motivated by this progress, we provide…


[Phys. Rev. B 108, 134513] Published Mon Oct 23, 2023

Homotopic classification of band structures: Stable, fragile, delicate, and stable representation-protected topology
Piet W. Brouwer and Vatsal Dwivedi
Author(s): Piet W. Brouwer and Vatsal Dwivedi

Fragile and delicate topological phases of noninteracting fermions can be trivialized under addition of trivial bands, in contrast to strong topological phases. Here, the authors describe a classification procedure based on homotopy theory for topological insulators with a fixed number of bands. They thereby classify band structures symmetric under discrete rotations and time-reversal at the highest possible level of granularity and identify instances of “representation-protected stable topology”, which is robust to addition of trivial bands with a fixed orbital type.


[Phys. Rev. B 108, 155137] Published Mon Oct 23, 2023

Entanglement signatures of multipolar higher-order topological phases
Oleg Dubinkin and Taylor L. Hughes
Author(s): Oleg Dubinkin and Taylor L. Hughes

We propose a procedure that characterizes free-fermion or interacting classes of higher-order topological phases via their bulk entanglement structure. To this end, we construct nested entanglement Hamiltonians by first applying an entanglement cut to the ordinary many-body ground state, and then it…


[Phys. Rev. B 108, 155138] Published Mon Oct 23, 2023

Transport in strained graphene: Interplay of Abelian and axial magnetic fields
Aqeel Ahmed, Sanjib Kumar Das, and Bitan Roy
Author(s): Aqeel Ahmed, Sanjib Kumar Das, and Bitan Roy

Immersed in external magnetic fields $(B)$, buckled graphene constitutes an ideal tabletop setup, manifesting a confluence of time-reversal symmetry $(\mathcal{T})$ breaking Abelian $(B)$ and $\mathcal{T}$-preserving strain-induced internal axial $(b)$ magnetic fields. In such a system, here we nume…


[Phys. Rev. B 108, 155426] Published Mon Oct 23, 2023

Seebeck and Nernst effects of pseudospin-1 fermions in the $α−{T}_{3}$ model under magnetic fields
Wenye Duan
Author(s): Wenye Duan

We numerically study the Seebeck and Nernst effects of pseudospin-1 fermions in the $α−{T}_{3}$ model under magnetic fields by combining the nonequilibrium Green's function and the Landauer-Büttiker formalism with the Stréda formula. In the $α=0$ limit under strong magnetic fields, our results are i…


[Phys. Rev. B 108, 155428] Published Mon Oct 23, 2023

Intrinsic surface superconducting instability in type-I Weyl semimetals
Aymen Nomani and Pavan Hosur
Author(s): Aymen Nomani and Pavan Hosur

Recent experiments on nonmagnetic Weyl semimetals have seen separate bulk and surface superconductivity in Weyl semimetals, which raises the question of whether the surface Fermi arcs can support intrinsic superconductivity while the bulk stays in the normal state. A theoretical answer to this quest…


[Phys. Rev. B 108, 165144] Published Mon Oct 23, 2023

Understanding the large shift photocurrent of ${\mathrm{WS}}_{2}$ nanotubes: A comparative analysis with monolayers
Jyoti Krishna, Peio Garcia-Goiricelaya, Fernando de Juan, and Julen Ibañez-Azpiroz
Author(s): Jyoti Krishna, Peio Garcia-Goiricelaya, Fernando de Juan, and Julen Ibañez-Azpiroz

We study the similarities and differences in the shift photocurrent contribution to the bulk photovoltaic effect between transition-metal dichalcogenide monolayers and nanotubes. Our analysis is based on density functional theory in combination with the Wannier interpolation technique for the calcul…


[Phys. Rev. B 108, 165418] Published Mon Oct 23, 2023

Emergent charge density wave order in the monolayer limit of $1T\text{−}{\mathrm{TiTe}}_{2}$ and $1T\text{−}{\mathrm{ZrTe}}_{2}$
Jiayuan Zhang, Fei Wang, and Chao-Sheng Lian
Author(s): Jiayuan Zhang, Fei Wang, and Chao-Sheng Lian

A peculiar charge-density wave (CDW) phase, absent in the bulk, has been widely studied in monolayer $1T\text{−}{\mathrm{TiTe}}_{2}$ and newly observed in monolayer $1T\text{−}{\mathrm{ZrTe}}_{2}$, while its origin and physical properties remain unclear. Here, we study the distorted lattice and asso…


[Phys. Rev. B 108, 165421] Published Mon Oct 23, 2023

$SO(8)$ unification and the large-$N$ theory of superconductor-insulator transition of two-dimensional Dirac fermions
Igor F. Herbut and Subrata Mandal
Author(s): Igor F. Herbut and Subrata Mandal

Electrons on honeycomb or pi-flux lattices obey the effective massless Dirac equation at low energies and at the neutrality point, and should suffer quantum phase transitions into various Mott insulators and superconductors at strong two-body interactions. We show that 35 out of 36 such order parame…


[Phys. Rev. B 108, L161108] Published Mon Oct 23, 2023

Found 2 papers in prl
Date of feed: Tue, 24 Oct 2023 03:16:59 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)

Titania Mixed with Silica: A Low Thermal-Noise Coating Material for Gravitational-Wave Detectors
Graeme I. McGhee, Viola Spagnuolo, Nicholas Demos, Simon C. Tait, Peter G. Murray, Martin Chicoine, Paul Dabadie, Slawek Gras, Jim Hough, Guido Alex Iandolo, Ross Johnston, Valérie Martinez, Oli Patane, Sheila Rowan, François Schiettekatte, Joshua R. Smith, Lukas Terkowski, Liyuan Zhang, Matthew Evans, Iain W. Martin, and Jessica Steinlechner
Author(s): Graeme I. McGhee, Viola Spagnuolo, Nicholas Demos, Simon C. Tait, Peter G. Murray, Martin Chicoine, Paul Dabadie, Slawek Gras, Jim Hough, Guido Alex Iandolo, Ross Johnston, Valérie Martinez, Oli Patane, Sheila Rowan, François Schiettekatte, Joshua R. Smith, Lukas Terkowski, Liyuan Zhang, Matthew Evans, Iain W. Martin, and Jessica Steinlechner

Coating thermal noise is one of the dominant noise sources in current gravitational wave detectors and ultimately limits their ability to observe weaker or more distant astronomical sources. This Letter presents investigations of ${\mathrm{TiO}}_{2}$ mixed with ${\mathrm{SiO}}_{2}$ (${\mathrm{TiO}}_…


[Phys. Rev. Lett. 131, 171401] Published Mon Oct 23, 2023

Complete Crystalline Topological Invariants from Partial Rotations in $(2+1)\mathrm{D}$ Invertible Fermionic States and Hofstadter’s Butterfly
Yuxuan Zhang, Naren Manjunath, Ryohei Kobayashi, and Maissam Barkeshli
Author(s): Yuxuan Zhang, Naren Manjunath, Ryohei Kobayashi, and Maissam Barkeshli

The theory of topological phases of matter predicts invariants protected only by crystalline symmetry, yet it has been unclear how to extract these from microscopic calculations in general. Here, we show how to extract a set of many-body invariants ${{\mathrm{Θ}}_{o}^{±}}$, where $o$ is a high symme…


[Phys. Rev. Lett. 131, 176501] Published Mon Oct 23, 2023

Found 2 papers in pr_res
Date of feed: Tue, 24 Oct 2023 03:17:00 GMT

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

Quadrature skyrmions in two-dimensionally arrayed parametric resonators
Hiroshi Yamaguchi, Daiki Hatanaka, and Motoki Asano
Author(s): Hiroshi Yamaguchi, Daiki Hatanaka, and Motoki Asano

Skyrmions are topological solitons in two-dimensional systems and have been observed in various physical systems. Generating and controlling skyrmions in artificial resonator arrays lead to novel acoustic, photonic, and electric devices, but it is a challenge to implement a vector variable with the …


[Phys. Rev. Research 5, 043076] Published Mon Oct 23, 2023

Quantum phase transition between symmetry enriched topological phases in tensor-network states
Lukas Haller, Wen-Tao Xu, Yu-Jie Liu, and Frank Pollmann
Author(s): Lukas Haller, Wen-Tao Xu, Yu-Jie Liu, and Frank Pollmann

Quantum phase transitions between different topologically ordered phases exhibit rich structures and are generically challenging to study in microscopic lattice models. In this paper, we propose a tensor-network solvable model that allows us to tune between different symmetry enriched topological (S…


[Phys. Rev. Research 5, 043078] Published Mon Oct 23, 2023