Found 29 papers in cond-mat
Date of feed: Mon, 29 May 2023 00:30:00 GMT

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Multifunctional, Self-Cleaning Air Filters Based on Graphene-Enhanced Ceramic Networks. (arXiv:2305.16374v1 [physics.soc-ph])
Armin Reimers, Ala Bouhanguel, Erik Greve, Morten Möller, Lena Marie Saure, Sören Kaps, Lasse Wegner, Ali Shaygan Nia, Xinliang Feng, Fabian Schütt, Yves Andres, Rainer Adelung

Particulate air pollution is taking a huge toll on modern society, being associated with more than three million deaths per year. In addition, airborne infectious microorganism can spread dangerous diseases, further elevating the problem. A common way to mitigate the risks of airborne particles is by air filtration. However, conventional air filters usually do not provide any functionality beyond particle removal. They are unable to inactivate accumulated contaminants and therefore need periodic maintenance and replacement to remain operational and safe. This work presents a multifunctional, self-cleaning air filtration system which utilizes a novel graphene-enhanced air filter medium (GeFM). The hybrid network of the GeFM combines the passive structure-based air filtration properties of an underlying ceramic network with additional active features based on the functional properties of a graphene thin film. The GeFM is able to capture >95 % of microorganisms and particles larger than 1 $\mu$m and can be repetitively Joule-heated to >300 {\deg}C for several hours without signs of degradation. Hereby, built-up organic particulate matter and microbial contaminants are effectively decomposed, regenerating the GeFM. Additionally, the GeFM provides unique options to monitor the filter's air troughput and loading status during operation. The active features of the GeFM can drastically improve filter life-time and safety, offering great potential for the development of safer and more sustainable air filtration solutions to face the future challenges of air pollution and pandemics.


Boundary Strong Zero Modes. (arXiv:2305.16382v1 [quant-ph])
Christopher T. Olund, Norman Y. Yao, Jack Kemp

Strong zero modes are edge-localized degrees of freedom capable of storing information at infinite temperature, even in systems with no disorder. To date, their stability has only been systematically explored at the physical edge of a system. Here, we extend the notion of strong zero modes to the boundary between two systems, and present a unifying framework for the stability of these boundary strong zero modes. Unlike zero-temperature topological edge modes, which are guaranteed to exist at the interface between a trivial and topological phase, the robustness of boundary strong zero modes is significantly more subtle. This subtlety is perhaps best illustrated by the following dichotomy: we find that the interface between a trivial and ordered phase does not guarantee the existence of a strong zero mode, while the interface between two ordered phases can, in certain cases, lead to an exact strong zero mode.


Magic Angle Butterfly in Twisted Trilayer Graphene. (arXiv:2305.16385v1 [cond-mat.str-el])
Fedor K. Popov, Grigory Tarnopolsky

We consider a configuration of three stacked graphene monolayers with commensurate twist angles $\theta_{12}/\theta_{23}=p/q$, where $p$ and $q$ are coprime integers with $0<p<|q|$ and $q$ can be positive or negative. We study this system using the continuum model in the chiral limit when interlayer coupling terms between $\textrm{AA}_{12}$ and $\textrm{AA}_{23}$ sites of the moir\'{e} patterns $12$ and $23$ are neglected. There are only three inequivalent displacements between the moir\'{e} patterns $12$ and $23$, at which the three monolayers' Dirac zero modes are protected. Remarkably, for these displacements and an arbitrary $p/q$ we discover exactly flat bands at an infinite set of twist angles (magic angles). We provide theoretical explanation and classification of all possible configurations and topologies of the flat bands.


Topological Phases with Average Symmetries: the Decohered, the Disordered, and the Intrinsic. (arXiv:2305.16399v1 [cond-mat.str-el])
Ruochen Ma, Jian-Hao Zhang, Zhen Bi, Meng Cheng, Chong Wang

Global symmetries greatly enrich the landscape of topological quantum phases, playing an essential role from symmetry-protection of topological insulators to symmetry charge fractionalization on anyons in fractional quantum Hall effect. Topological phases in mixed quantum states, originating from decoherence in open quantum systems or disorders in imperfect crystalline solids, have recently garnered significant interest. Unlike pure states, mixed quantum states can exhibit average symmetries -- symmetries that keep the total ensemble invariant but not on each individual state. It was realized that symmetry-protected topological phases could be well-defined for such mixed states carrying average symmetries. In this work, we present a systematic classification and characterization of average symmetry-protected topological (ASPT) phases applicable to generic symmetry groups, encompassing both average and exact symmetries, for bosonic and fermionic systems. Moreover, we formulate the theory of average symmetry-enriched topological (ASET) orders in disordered bosonic systems. We demonstrate that numerous concepts from pure state symmetry-enriched topological (SET) phases, such as anyon permutation, symmetry fractionalization, and 't Hooft anomaly, are well-defined for ASET phases but with various intriguing twists. Our systematic approach helps clarify nuanced issues in previous literature and uncovers compelling new physics.


Type-II Dirac points and Dirac nodal loops on the magnons of square-hexagon-octagon lattice. (arXiv:2305.16419v1 [cond-mat.mes-hall])
Meng-Han Zhang, Dao-Xin Yao

We study topological magnons on an anisotropic square-hexagon-octagon (SHO) lattice which has been found by a two-dimensional Biphenylene network (BPN). We propose the concepts of type-II Dirac magnonic states where new schemes to achieve topological magnons are unfolded without requiring the Dzyaloshinsky-Moriya interactions (DMIs). In the ferromagnetic states, the topological distinctions at the type-II Dirac points along with one-dimensional (1D) closed lines of Dirac magnon nodes are characterized by the $\mathbb{Z}_2$ invariant. We find pair annihilation of the Dirac magnons and use the Wilson loop method to depict the topological protection of the band-degeneracy. The Green's function approach is used to calculte chiral edge modes and magnon density of states (DOS). We introduce the DMIs to gap the type-II Dirac magnon points and demonstrate the Dirac nodal loops (DNLs) are robust against the DMIs within a certain parameter range. The topological phase diagram of magnon bands is given via calculating the Berry curvature and Chern number. We find that the anomalous thermal Hall conductivity gives connection to the magnon edge current. Furthermore, we derive the differential gyromagnetic ratio to exhibit the Einstein-de Haas effect (EdH) of magnons with topological features.


Modeling of experimentally observed topological defects inside bulk polycrystals. (arXiv:2305.16454v1 [cond-mat.mtrl-sci])
Siddharth Singh, He Liu, Rajat Arora, Robert M. Suter, Amit Acharya

A rigorous methodology is developed for computing elastic fields generated by experimentally observed defect structures within grains in a polycrystal that has undergone tensile extension. An example application is made using a near-field High Energy X-ray Diffraction Microscope measurement of a zirconium sample that underwent $13.6\%$ tensile extension from an initially well-annealed state. (Sub)grain boundary features are identified with apparent disclination line defects in them. The elastic fields of these features identified from the experiment are calculated.


Lieb-Schultz-Mattis Theorem in Open Quantum Systems. (arXiv:2305.16496v1 [cond-mat.stat-mech])
Kohei Kawabata, Ramanjit Sohal, Shinsei Ryu

The Lieb-Schultz-Mattis (LSM) theorem provides a general constraint on quantum many-body systems and plays a significant role in the Haldane gap phenomena and topological phases of matter. Here, we extend the LSM theorem to open quantum systems and establish a general theorem that restricts the steady state and spectral gap of Liouvillians based solely on symmetry. Specifically, we demonstrate that the unique gapped steady state is prohibited when translation invariance and $\mathrm{U} \left( 1 \right)$ symmetry are simultaneously present for noninteger filling numbers. As an illustrative example, we find that no dissipative gap is open in the spin-$1/2$ dissipative Heisenberg model while a dissipative gap can be open in the spin-$1$ counterpart -- an analog of the Haldane gap phenomena in open quantum systems. Furthermore, we show that the LSM constraint manifests itself in a quantum anomaly of the dissipative form factor of Liouvillians. We also find the LSM constraints due to symmetry intrinsic to open quantum systems, such as Kubo-Martin-Schwinger symmetry.


Topotactic Transition: A Promising Opportunity for Creating New Oxides. (arXiv:2305.16605v1 [cond-mat.mtrl-sci])
Ziang Meng, Han Yan, Peixin Qin, Xiaorong Zhou, Xiaoning Wang, Hongyu Chen, Li Liu, Zhiqi Liu

Topotactic transition is a structural phase change in a matrix crystal lattice mediated by the ordered loss/gain and rearrangement of atoms, leading to unusual coordination environments and metal atoms with rare valent states. As early as in 1990s, low temperature hydride reduction was utilized to realize the topotactic transition. Since then, topological transformations have been developed via multiple approaches. Especially, the recent discovery of the Ni-based superconductivity in infinite-layer nickelates has greatly boosted the topotactic transition mean to synthesizing new oxides for exploring exotic functional properties. In this review, we have provided a detailed and generalized introduction to oxygen-related topotactic transition. The main body of our review include four parts: the structure-facilitated effects, the mechanism of the topotactic transition, some examples of topotactic transition methods adopted in different metal oxides (V, Mn, Fe, Co, Ni) and the related applications. This work is to provide timely and thorough strategies to successfully realize topotactic transitions for researchers who are eager to create new oxide phases or new oxide materials with desired functions.


Lattice distortions, moir\'e phonons, and relaxed electronic band structures in magic-angle twisted bilayer graphene. (arXiv:2305.16640v1 [cond-mat.mes-hall])
Bo Xie, Jianpeng Liu

In this work, we present a theoretical research on the lattice relaxations, phonon properties, and relaxed electronic structures in magic-angle twisted bilayer graphene (TBG). We construct a continuum elastic model in order to study the lattice dynamics of magic-angle TBG, where both in-plane and out-of-plane lattice displacements are take into account. The fully relaxed lattice structure calculated using such a model is in quantitative agreement with experimental measurements. Furthermore, we investigate the phonon properties in magic-angle TBG using the continuum elastic model, where both the in-plane and out-of-plane phonon modes are included and treated on equal footing. We identify different types of moir\'e phonons including in-plane sliding modes, soft out-of-plane flexural modes, as well as out-of-plane breathing modes. The latter two types of phonon modes exhibit interesting monopolar, dipolar, quadrupolar, and octupolar-type out-of-plane vibration patterns. Additionally, we explore the impact of the relaxed moir\'e superlattice structure on the electronic band structures of magic-angle TBG using an effective continuum model, which shows nearly exact agreement with those calculated using a microscopic atomistic tight-binding approach. Our work lays foundation for further studies on the electron-phonon coupling effects and their interplay with $e$-$e$ interactions in magic-angle TBG.


Experimental demonstration of robotic active matter micellization. (arXiv:2305.16659v1 [cond-mat.soft])
Anastasia A. Molodtsova, Mikhail K. Buzakov, Alina D. Rozenblit, Vyacheslav A. Smirnov, Daria V. Sennikova, Vadim A. Porvatov, Oleg I. Burmistrov, Ekaterina M. Puhtina, Alexey A. Dmitriev, Nikita A. Olekhno

Active matter composed of self-propelled particles features a fascinating set of self-organization phenomena, spanning from motility-induced phase separation to phototaxis to topological excitations depending on the nature and parameters of the system. In the present Letter, we consider the formation of micelles from particles with a broken symmetry having a circular back and a sharpened nose and moving towards the cusp. As we demonstrate in experiments with robotic swarms, such particles can either remain in the isotropic phase or form micelles depending on the location of their center of inertia in accordance with a recent theoretical proposal [T. Kruglov, A. Borisov, Particles 2021 (2021)]. Crucially, the predicted micellization does not involve any charge asymmetry, in contrast to that observed in surfactants, and is governed by an interplay of activity and particle shape asymmetry. This renders the observed ordering reversible upon switching of the particles' activity and opens the route towards novel applications in tunable structuring of materials.


Rotation of gap nodes in the topological superconductor Cu$_x$(PbSe)$_5$(Bi$_2$Se$_3$)$_6$. (arXiv:2305.16732v1 [cond-mat.supr-con])
Mahasweta Bagchi, Jens Brede, Aline Ramires, Yoichi Ando

Among the family of odd-parity topological superconductors derived from Bi$_2$Se$_3$, Cu$_x$(PbSe)$_5$(Bi$_2$Se$_3$)$_6$ has been elucidated to have gap nodes. Although the nodal gap structure has been established by specific-heat and thermal-conductivity measurements, there has been no direct observation of the superconducting gap of CPSBS using scanning tunnelling spectroscopy (STS). Here we report the first STS experiments on CPSBS down to 0.35 K, which found that the vortices generated by out-of-plane magnetic fields have an elliptical shape, reflecting the anisotropic gap structure. The orientation of the gap minima is found to be aligned with the bulk direction when the surface lattice image shows twofold symmetry, but, surprisingly, it is rotated by 30$^{\circ}$ when twofold symmetry is absent. In addition, the superconducting gap spectra in zero magnetic field suggest that the gap nodes are most likely lifted. We argue that only an emergent symmetry at the surface, allowing for a linear superposition of gap functions with different symmetries, can lead to the rotation of the gap nodes. The absence of inversion symmetry at the surface additionally lifts the nodes. This result establishes the subtle but crucial role of crystalline symmetry in topological superconductivity.


Quantum field theoretical framework for the electromagnetic response of graphene and dispersion relations with implications to the Casimir effect. (arXiv:2305.16762v1 [quant-ph])
G. L. Klimchitskaya, V. M. Mostepanenko

The spatially nonlocal response functions of graphene obtained on the basis of first principles of quantum field theory using the polarization tensor are considered in the areas of both the on-the-mass-shell and off-the-mass-shell waves. It s shown that at zero frequency the longitudinal permittivity of graphene is the regular function, whereas the transverse one possesses a double pole for any nonzero wave vector. According to our results, both the longitudinal and transverse permittivities satisfy the dispersion (Kramers-Kronig) relations connecting their real and imaginary parts, as well as expressing each of these permittivities along the imaginary frequency axis via its imaginary part. For the transverse permittivity, the form of an additional term arising in the dispersion relations due to the presence of a double pole is found. The form of dispersion relations is unaffected by the branch points which arise on the real frequency axis in the presence of spatial nonlocality. The obtained results are discussed in connection with the well known problem of the Lifshitz theory which was found to be in conflict with the measurement data when using the much studied response function of metals. A possible way of attack on this problem based on the case of graphene is suggested.


Strong magnetic proximity effect in Van der Waals heterostructures driven by direct hybridization. (arXiv:2305.16813v1 [cond-mat.mes-hall])
C. Cardoso, A. T. Costa, A. H. MacDonald, J. Fernández-Rossier

We propose a new class of magnetic proximity effects based on the spin dependent hybridization between the electronic states at the Fermi energy in a non-magnetic conductor and the narrow spin split bands of a ferromagnetic insulator. Unlike conventional exchange proximity, we show this hybridization proximity effect has a very strong influence on the non-magnetic layer and can be further modulated by application of an electric field. We use DFT calculations to illustrate this effect in graphene placed next to a monolayer of CrI$_3$, a ferromagnetic insulator. We find strong hybridization of the graphene bands with the narrow conduction band of CrI$_3$ in one spin channel only. We show that our results are robust with respect to lattice mismatch and twist angle variations. Furthermore, we show that an out-of-plane electric field can be used to modulate the hybridization strength, paving the way for applications.


Room temperature quantum Hall effect in a gated ferroelectric-graphene heterostructure. (arXiv:2305.16825v1 [cond-mat.mes-hall])
Anubhab Dey, Nathan Cottam, Oleg Makarovskiy, Wenjing Yan, Vaidotas Mišeikis, Camilla Coletti, James Kerfoot, Vladimir Korolkov, Laurence Eaves, Jasper F. Linnartz, Arwin Kool, Steffen Wiedmann, Amalia Patanè

The quantum Hall effect is widely used for the investigation of fundamental phenomena, ranging from topological phases to composite fermions. In particular, the discovery of a room temperature resistance quantum in graphene is significant for compact resistance standards that can operate above cryogenic temperatures. However, this requires large magnetic fields that are accessible only in a few high magnetic field facilities. Here, we report on the quantum Hall effect in graphene encapsulated by the ferroelectric insulator CuInP2S6. Electrostatic gating of the graphene channel enables the Fermi energy to be tuned so that electrons in the localized states of the insulator are in equilibrium with the current-carrying, delocalized states of graphene. Due to the presence of strongly bound states in this hybrid system, a quantum Hall plateau can be achieved at room temperature in relatively modest magnetic fields. This phenomenon offers the prospect for the controlled manipulation of the quantum Hall effect at room temperature.


Shift photoconductivity in the Haldane model. (arXiv:2305.17035v1 [cond-mat.mes-hall])
Javier Sivianes (1), Julen Ibañez-Azpiroz (1 and 2) ((1) Centro de Física de Materiales (CSIC-UPV/EHU), Donostia-San Sebastián, Spain, (2) Ikerbasque Foundation, Bilbao, Spain)

The shift current is part of the second-order optical response of materials with a close connection to topology. Here we report a sign inversion in the band-edge shift photoconductivity of the Haldane model when the system undergoes a topological phase transition. This result is obtained following two complementary schemes. On one hand, we derive an analytical expression for the band-edge shift current in a two-band tight-binding model showing that the sign reversal is driven by the mass term. On the other hand, we perform a numerical evaluation on a continuum version of the Haldane model. This approach allows us to include off-diagonal matrix elements of the position operator, which are discarded in tight-binding models but can contribute significantly to the shift current. Explicit evaluation of the shift current shows that while the model predictions remain accurate in the deep tight-binding regime, significant deviations arise for shallow potential landscapes. Notably, the sign reversal across the topological phase transition is observed in all regimes, implying it is a robust effect that could be observable in a wide range of topological insulators such as $\text{BiTe}_{2}$ and $\text{CsPbI}_{3}$ reported in Phys. Rev. Lett. 116, 237402 (2016).


Directional effects of antiferromagnetic ordering on the electronic structure in NdSb. (arXiv:2305.17085v1 [cond-mat.str-el])
Yevhen Kushnirenko, Brinda Kuthanazhi, Lin-Lin Wang, Benjamin Schrunk, Evan O'Leary, Andrew Eaton, P. C. Canfield, Adam Kaminski

The recent discovery of unconventional surface state pairs, which give rise to Fermi arcs and spin textures, in antiferromagnetically ordered NdBi raised the interest in rare-earth monopnictides. Several scenarios of antiferromagnetic order have been suggested to explain the origin of these states with some of them being consistent with the presence of non-trivial topologies. In this study, we use angle-resolved photoemission spectroscopy (ARPES) and density-functional-theory (DFT) calculations to investigate the electronic structure of NdSb. We found the presence of distinct domains that have different electronic structure at the surface. These domains correspond to different orientations of magnetic moments in the AFM state with respect to the surface. We demonstrated remarkable agreement between DFT calculations and ARPES that capture all essential changes in the band structure caused by transition to a magnetically ordered state.


Direct visualization of the charge transfer in Graphene/$\alpha$-RuCl$_3$ heterostructure. (arXiv:2305.17130v1 [cond-mat.mtrl-sci])
Antonio Rossi, Riccardo Dettori, Cameron Johnson, Jesse Balgley, John C. Thomas, Luca Francaviglia, Andreas K. Schmid, Kenji Watanabe, Takashi Taniguchi, Matthew Cothrine, David G. Mandrus, Chris Jozwiak, Aaron Bostwik, Erik A. Henriksen, Alexander Weber-Bargioni, Eli Rotenberg

We investigate the electronic properties of a graphene and $\alpha$-ruthenium trichloride (hereafter RuCl$_3$) heterostructure, using a combination of experimental and theoretical techniques. RuCl$_3$ is a Mott insulator and a Kitaev material, and its combination with graphene has gained increasing attention due to its potential applicability in novel electronic and optoelectronic devices. By using a combination of spatially resolved photoemission spectroscopy, low energy electron microscopy, and density functional theory (DFT) calculations we are able to provide a first direct visualization of the massive charge transfer from graphene to RuCl$_3$, which can modify the electronic properties of both materials, leading to novel electronic phenomena at their interface. The electronic band structure is compared to DFT calculations that confirm the occurrence of a Mott transition for RuCl$_3$. Finally, a measurement of spatially resolved work function allows for a direct estimate of the interface dipole between graphene and RuCl$_3$. The strong coupling between graphene and RuCl$_3$ could lead to new ways of manipulating electronic properties of two-dimensional lateral heterojunction. Understanding the electronic properties of this structure is pivotal for designing next generation low-power opto-electronics devices.


Holographic dissipation prefers the Landau over the Keldysh form. (arXiv:2207.02814v3 [hep-th] UPDATED)
Yu-Kun Yan, Shanquan Lan, Yu Tian, Peng Yang, Shunhui Yao, Hongbao Zhang

Although holographic duality has been regarded as a complementary tool in helping understand the non-equilibrium dynamics of strongly coupled many-body systems, it still remains a remarkable challenge how to confront its predictions quantitatively with the real experimental scenarios. By matching the holographic vortex dynamics with the phenomenological dissipative Gross-Pitaeviskii models, we find that the holographic dissipation mechanism can be well captured by the Landau form rather than the Keldysh one, although the latter is much more widely used in numerical simulations. Our finding is expected to open up novel avenues for facilitating the quantitative test of the holographic predictions against the upcoming experimental data. Our result also provides a prime example how holographic duality can help select proper phenomenological models to describe far-from-equilibrium nonlinear dynamics beyond the hydrodynamic regime.


Unconventional higher-order topology in quasicrystals. (arXiv:2209.05751v2 [cond-mat.mtrl-sci] UPDATED)
Aoqian Shi, Yiwei Peng, Jiapei Jiang, Yuchen Peng, Peng Peng, Jianzhi Chen, Hongsheng Chen, Shuangchun Wen, Xiao Lin, Fei Gao, Jianjun Liu

Conventional two-dimensional (2D) higher-order topological insulators are characterized by higher-order topological states at the outer boundary of non-trivial regions, that is, 0D topological corner states (TCSs). In this Letter, it is found that the higher-order topological quasicrystalline insulators (HOTQIs) have non-0D TCSs arrays at the outer and inner boundaries, which breaks through the limitation of bulk-edge-corner correspondence (corresponding dimension is 2D-1D-0D). The universal theoretical framework of the multimer analysis method is improved and the difference in the average charge density is proposed as the real-space topological index, which effectively characterizes the unconventional higher-order topology in HOTQIs. Furthermore, HOTQIs and their non-0D TCSs arrays in photonic system are experimentally observed for the first time. These results offer a promising avenue for investigating TCSs with high integration and multi-region distribution and pave the way for exploring the topological phenomena and applications of photonic and phononic quasicrystals.


Superconductivity and correlated phases in non-twisted bilayer and trilayer graphene. (arXiv:2211.02880v2 [cond-mat.mes-hall] UPDATED)
Pierre A. Pantaleon, Alejandro Jimeno-Pozo, Hector Sainz-Cruz, Vo Tien Phong, Tommaso Cea, Francisco Guinea

Twisted bilayer graphene has a rich phase diagram, including superconductivity. Recently, an unexpected discovery has been the observation of superconductivity in non-twisted graphene bilayers and trilayers. In this Perspective, we give an overview of the search for uncommon phases in non-twisted graphene systems. We first contextualize these recent results within earlier work in the field, before examining the new experimental findings. Finally, we analyse the numerous theoretical models that study the underlying physical processes in these systems


Quantum phase slips in a resonant Josephson junction. (arXiv:2211.05660v3 [cond-mat.mes-hall] UPDATED)
Tereza Vakhtel, Bernard van Heck

We investigate the consequences of resonant tunneling of Cooper pairs on the quantum phase slips occurring in a Josephson junction. The amplitude for quantum tunneling under the Josephson potential barrier is modified by the Landau-Zener amplitude of adiabatic passage through an Andreev level crossing, resulting in the suppression of $2\pi$ phase slips. As a consequence, close to resonance, $4\pi$ phase slips become the dominant tunneling process. We illustrate this crossover by determining the energy spectrum of a transmon circuit, showing that a residual charge dispersion persists even at perfect transparency.


Density-tuned effective metal-insulator transitions in 2D semiconductor layers: Anderson localization or Wigner crystallization. (arXiv:2211.10673v2 [cond-mat.mes-hall] UPDATED)
Seongjin Ahn, Sankar Das Sarma

Electrons (or holes) confined in 2D semiconductor layers have served as model systems for studying disorder and interaction effects for almost 50 years. In particular, strong disorder drives the metallic 2D carriers into a strongly localized Anderson insulator (AI) at low densities whereas pristine 2D electrons in the presence of no (or little) disorder should solidify into a Wigner crystal at low carrier densities. Since the disorder in 2D semiconductors is mostly Coulomb disorder arising from random charged impurities, the applicable physics is complex as the carriers interact with each other as well as with the random charged impurities through the same long-range Coulomb coupling. By critically theoretically analyzing the experimental transport data in depth using a realistic transport theory to calculate the low-temperature 2D resistivity as a function of carrier density in 11 different experimental samples covering 9 different materials, we establish, utilizing the Ioffe-Regel-Mott criterion for strong localization, a direct connection between the critical localization density for the 2D metal-insulator transition (MIT) and the sample mobility deep into the metallic state, which for clean samples could lead to a localization density low enough to make the transition appear to be a Wigner crystallization. We believe that the insulating phase is always an effective Coulomb disorder-induced localized AI, which may have short-range WC-like correlations at low carrier densities. Our theoretically calculated disorder-driven critical MIT density agrees with experimental findings in all 2D samples, even for the ultra-clean samples. In particular, the extrapolated critical density for the 2D MIT seems to vanish when the high-density mobility goes to infinity, indicating that transport probes a disorder-localized insulating ground state independent of how low the carrier density might be.


Production of lattice gauge-Higgs topological states in measurement-only quantum circuit. (arXiv:2302.13692v2 [cond-mat.stat-mech] UPDATED)
Yoshihito Kuno, Ikuo Ichinose

By imaginary-time evolution with Hamiltonian, an arbitrary state arrives in the system's ground state. In this work, we conjecture that this dynamics can be simulated by measurement-only circuit (MoC), where each projective measurement is set in a suitable way. Based on terms in the Hamiltonian and ratios of their parameters (coefficients), we propose a guiding principle for the choice of the measured operators called stabilizers and also the probability of projective measurement in the MoC. In order to examine and verify this conjecture of the parameter ratio and probability ratio correspondence in a practical way, we study a generalized (1+1)-dimensional $Z_2$ lattice gauge-Higgs model, whose phase diagram is very rich including symmetry-protected topological phase, deconfinement phase, etc. We find that the MoC constructed by the guiding principle reproduces phase diagram very similar to that of the ground state of the gauge-Higgs Hamiltonian. The present work indicates that the MoC can be broadly used to produce interesting phases of matter, which are difficult to be simulated by ordinary Hamiltonian systems composed of stabilizer-type terms.


Non-Fermi Liquids from Dipolar Symmetry Breaking. (arXiv:2304.01181v2 [cond-mat.str-el] UPDATED)
Amogh Anakru, Zhen Bi

The emergence of fractonic topological phases and novel universality classes for quantum dynamics highlights the importance of dipolar symmetry in condensed matter systems. In this work, we study the properties of symmetry-breaking phases of the dipolar symmetries in fermionic models in various spatial dimensions. In such systems, fermions obtain energy dispersion through dipole condensation. Due to the nontrivial commutation between the translation symmetry and dipolar symmetry, the Goldstone modes of the dipolar condensate are strongly coupled to the dispersive fermions and naturally give rise to non-Fermi liquids at low energies. The IR description of the dipolar symmetry-breaking phase is analogous to the well-known theory of a Fermi surface coupled to an emergent U(1) gauge field. We also discuss the crossover behavior when the dipolar symmetry is slightly broken and the cases with anisotropic dipolar conservation.


Interplay between lattice gauge theory and subsystem codes. (arXiv:2304.05718v2 [cond-mat.stat-mech] UPDATED)
Yoshihito Kuno, Ikuo Ichinose

It is now widely recognized that the toric code is a pure gauge-theory model governed by a projective Hamiltonian with topological orders. In this work, we extend the interplay between quantum information system and gauge-theory model from the view point of subsystem code, which is suitable for \textit{gauge systems including matter fields}. As an example, we show that $Z_2$ lattice gauge-Higgs model in (2+1)-dimensions with specific open boundary conditions is noting but a kind of subsystem code. In the system, Gauss-law constraints are stabilizers, and order parameters identifying Higgs and confinement phases exist and they are nothing but logical operators in subsystem codes residing on the boundaries. Mixed anomaly of them dictates the existence of boundary zero modes, which is a direct consequence of symmetry-protected topological order in Higgs and confinement phases. After identifying phase diagram, subsystem codes are embedded in the Higgs and confinement phases. As our main findings, we give an explicit description of the code (encoded qubit) in the Higgs and confinement phases, which clarifies duality between Higgs and confinement phases. The degenerate structure of subsystem code in the Higgs and confinement phases remains even in very high-energy levels, which is analogous to notion of strong-zero modes observed in some interesting condensed-matter systems. Numerical methods are used to corroborate analytically-obtained results and the obtained spectrum structure supports the analytical description of various subsystem codes in the gauge theory phases.


A note on GMP algebra, dipole symmetry, and Hohenberg-Mermin-Wagner theorem in the lowest Landau level. (arXiv:2304.09927v2 [cond-mat.str-el] UPDATED)
Lev Spodyneiko

After projection to the lowest Landau level translational invariance and particle conservation combine into dipole symmetry. We show that the new symmetry forbids spontaneous $U(1)$ symmetry breaking at zero temperature. In the case of the spatially inhomogeneous magnetic field, where the translational invariance is absent, we show that the dipole symmetry disappears and the constraint on the symmetry breaking is lifted. We pay special attention to the fate of the Girvin-Macdonald-Platzman algebra in the inhomogeneous magnetic field and show that a natural generalization of it is still present even though the dipole symmetry is not.


Investigation of Spin-Wave Dynamics in Gyroid Nanostructures. (arXiv:2305.06319v2 [cond-mat.mes-hall] UPDATED)
Mateusz Gołębiewski, Riccardo Hertel, Vitaliy Vasyuchka, Mathias Weiler, Philipp Pirro, Maciej Krawczyk, Shunsuke Fukami, Hideo Ohno, Justin Llandro

A new concept in magnonics studies the dynamics of spin waves (SWs) in three-dimensional nanosystems. It is a natural evolution from conventionally used planar systems to explore magnetization configurations and dynamics in 3D nanostructures with lengths near intrinsic magnetic scales. In this work, we perform broadband ferromagnetic resonance (BBFMR) measurements and micromagnetic simulations of nanoscale magnetic gyroids - a periodic chiral structure consisting entirely of chiral triple junctions. Our results show unique properties of the network, such as the localization of the SW modes, evoking their topological properties, and the substantial sensitivity to the direction of the static magnetic field. The presented results open a wide range of applications in the emerging field of 3D magnonic crystals and spintronics.


Thermal conductivity of macroporous graphene aerogel measured using high resolution comparative infrared thermal microscopy. (arXiv:2305.09033v2 [physics.app-ph] UPDATED)
Jasmine M. Cox, Jessica J. Frick, Chen Liu, Zhou Li, Yaprak Ozbakir, Carlo Carraro, Roya Maboudian, Debbie G. Senesky

Graphene aerogel (GA) is a promising material for thermal management applications across many fields due to its lightweight and thermally insulative properties. However, standard values for important thermal properties, such as thermal conductivity, remain elusive due to the lack of reliable characterization techniques for highly porous materials. Comparative infrared thermal microscopy (CITM) is an attractive technique to obtain thermal conductance values of porous materials like GA, due to its non-invasive character, which requires no probing of, or contact with, the often-delicate structures and frameworks. In this study, we improve upon CITM by utilizing a higher resolution imaging setup and reducing the need for pore-filling coating of the sample (previously used to adjust for emissivity). This upgraded setup, verified by characterizing porous silica aerogel, allows for a more accurate confirmation of the fundamental thermal conductivity value of GA while still accounting for the thermal resistance at material boundaries. Using this improved method, we measure a thermal conductivity below 0.036 W/m$\cdot$K for commercial GA using multiple reference materials. These measurements demonstrate the impact of higher resolution thermal imaging to improve accuracy in low density, highly porous materials characterization. This study also reports thermal conductivity for much lower density (less than 15 mg/cm$^3$) GA than previously published studies while maintaining the robustness of the CITM technique.


Flat bands in bilayer graphene induced by proximity with polar $h$-BN superlattices. (arXiv:2305.09749v2 [cond-mat.mes-hall] UPDATED)
Marta Brzezińska, Oleg V. Yazyev

Motivated by the observation of polarization superlattices in twisted multilayers of hexagonal boron nitride ($h$-BN), we address the possibility of using these heterostructures for tailoring the properties of multilayer graphene by means of the electrostatic proximity effect. By using the combination of first-principles and large-scale tight-binding model calculations coupled via the Wannier function approach, we demonstrate the possibility of creating a sequence of well-separated flat-band manifolds in AB-stacked bilayer graphene at experimentally relevant superlattice periodicities above $\sim$30 nm. Our calculations show that the details of band structures depend on the local inversion symmetry breaking and the vertical electrical polarization, which are directly related to the atomic arrangement. The results advance the atomistic characterization of graphene-based systems in a superlattice potential beyond the continuum model.