Found 28 papers in cond-mat
Date of feed: Wed, 25 Oct 2023 00:30:00 GMT

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Tunable room temperature nonlinear Hall effect from the surfaces of elementary bismuth thin films. (arXiv:2310.15225v1 [cond-mat.mes-hall])
Pavlo Makushko, Sergey Kovalev, Yevhen Zabila, Igor Ilyakov, Alexey Ponomaryov, Atiqa Arshad, Gulloo Lal Prajapati, Thales V. A. G. de Oliveira, Jan-Christoph Deinert, Paul Chekhonin, Igor Veremchuk, Tobias Kosub, Yurii Skourski, Fabian Ganss, Denys Makarov, Carmine Ortix

The nonlinear Hall effect (NLHE) with time-reversal symmetry constitutes the appearance of a transverse voltage quadratic in the applied electric field. It is a second-order electronic transport phenomenon that induces frequency doubling and occurs in non-centrosymmetric crystals with large Berry curvature -- an emergent magnetic field encoding the geometric properties of electronic wavefunctions. The design of (opto)electronic devices based on the NLHE is however hindered by the fact that this nonlinear effect typically appears at low temperatures and in complex compounds characterized by Dirac or Weyl electrons. Here, we show a strong room temperature NLHE in the centrosymmetric elemental material bismuth synthesized in the form of technologically relevant polycrystalline thin films. The ($1\,1\,1$) surface electrons of this material are equipped with a Berry curvature triple that activates side jumps and skew scatterings generating nonlinear transverse currents. We also report a boost of the zero field nonlinear transverse voltage in arc-shaped bismuth stripes due to an extrinsic geometric classical counterpart of the NLHE. This electrical frequency doubling in curved geometries is then extended to optical second harmonic generation in the terahertz (THz) spectral range. The strong nonlinear electrodynamical responses of the surface states are further demonstrated by a concomitant highly efficient THz third harmonic generation which we achieve in a broad range of frequencies in Bi and Bi-based heterostructures. Combined with the possibility of growth on CMOS-compatible and mechanically flexible substrates, these results highlight the potential of Bi thin films for THz (opto)electronic applications.

A ballistic electron source with magnetically-controlled valley polarization in bilayer graphene. (arXiv:2310.15293v1 [cond-mat.mes-hall])
Josep Ingla-Aynés, Antonio L. R. Manesco, Talieh S. Ghiasi, Kenji Watanabe, Takashi Taniguchi, Herre S. J. van der Zant

The achievement of valley-polarized electron currents is a cornerstone for the realization of valleytronic devices. Here, we report on ballistic coherent transport experiments where two opposite quantum point contacts (QPCs) are defined by electrostatic gating in a bilayer graphene (BLG) channel. By steering the ballistic currents with an out-of-plane magnetic field we observe two current jets, a consequence of valley-dependent trigonal warping. Tuning the BLG carrier density and number of QPC modes (m) with a gate voltage we find that the two jets are present for m=1 and up to m=6, indicating the robustness of the effect. Semiclassical simulations which account for size quantization and trigonal warping of the Fermi surface quantitatively reproduce our data without fitting parameters, confirming the origin of the signals. In addition, our model shows that the ballistic currents collected for non-zero magnetic fields are valley-polarized independently of m, but their polarization depends on the magnetic field sign, envisioning such devices as ballistic current sources with tuneable valley-polarization.

Combining linear-scaling quantum transport and machine-learning molecular dynamics to study thermal and electronic transports in complex materials. (arXiv:2310.15314v1 [cond-mat.mtrl-sci])
Zheyong Fan, Yang Xiao, Yanzhou Wang, Penghua Ying, Shunda Chen, Haikuan Dong

We propose an efficient approach for simultaneous prediction of thermal and electronic transport properties in complex materials. Firstly, a highly efficient machine-learned neuroevolution potential is trained using reference data from quantum-mechanical density-functional theory calculations. This trained potential is then applied in large-scale molecular dynamics simulations, enabling the generation of realistic structures and accurate characterization of thermal transport properties. In addition, molecular dynamics simulations of atoms and linear-scaling quantum transport calculations of electrons are coupled to account for the electron-phonon scattering and other disorders that affect the charge carriers governing the electronic transport properties. We demonstrate the usefulness of this unified approach by studying thermoelectric transport properties of a graphene antidot lattice.

Quench-induced spontaneous currents in rings of ultracold fermionic atoms. (arXiv:2310.15348v1 [cond-mat.quant-gas])
Daniel G. Allman, Parth Sabharwal, Kevin C. Wright

We have measured the rate of spontaneous current formation in ring-shaped ensembles of fermionic $^6$Li atoms, following a thermal quench through the BCS superfluid phase transition. For the fastest quenches, the mean square winding number follows a scaling law with exponent $\sigma$ = 0.24(2), in line with predictions of the Kibble-Zurek (KZ) model for mean-field BCS theory. We use a hybrid quench protocol involving simultaneous evaporation and interaction ramps, with a long system lifetime allowing characterization of a different rate of spontaneous current formation in the slow-quench regime, where finite-size effects are important. Comparing our observations to a quasi-1D stochastic Ginzburg-Landau model, we find quantitative agreement for fast quenches, but only qualitative agreement for slow quenches.

Layer-by-Layer Assembled Nanowire Networks Enable Graph Theoretical Design of Multifunctional Coatings. (arXiv:2310.15369v1 [])
Wenbing Wu, Alain Kadar, Sang Hyun Lee, Bum Chul Park, Jeffery E. Raymond, Thomas K. Tsotsis, Carlos E. S. Cesnik, Sharon C. Glotzer, Valerie Goss, Nicholas A. Kotov

Multifunctional coatings are central for information, biomedical, transportation and energy technologies. These coatings must possess hard-to-attain properties and be scalable, adaptable, and sustainable, which makes layer-by-layer assembly (LBL) of nanomaterials uniquely suitable for these technologies. What remains largely unexplored is that LBL enables computational methodologies for structural design of these composites. Utilizing silver nanowires (NWs), we develop and validate a graph theoretical (GT) description of their LBL composites. GT successfully describes the multilayer structure with nonrandom disorder and enables simultaneous rapid assessment of several properties of electrical conductivity, electromagnetic transparency, and anisotropy. GT models for property assessment can be rapidly validated due to (1) quasi-2D confinement of NWs and (2) accurate microscopy data for stochastic organization of the NW networks. We finally show that spray-assisted LBL offers direct translation of the GT-based design of composite coatings to additive, scalable manufacturing of drone wings with straightforward extensions to other technologies.

Electric quadrupole second harmonic generation revealing dual magnetic orders in a magnetic Weyl semimetal. (arXiv:2310.15423v1 [cond-mat.mtrl-sci])
Youngjun Ahn, Xiaoyu Guo, Rui Xue, Kejian Qu, Kai Sun, David Mandrus, Liuyan Zhao

Broken symmetries and electronic topology are nicely manifested together in the second order nonlinear optical responses from topologically nontrivial materials. While second order nonlinear optical effects from the electric dipole (ED) contribution have been extensively explored in polar Weyl semimetals (WSMs) with broken spatial inversion (SI) symmetry, they are rarely studied in centrosymmetric magnetic WSMs with broken time reversal (TR) symmetry due to complete suppression of the ED contribution. Here, we report experimental demonstration of optical second harmonic generation (SHG) in a magnetic WSM Co$_{3}$Sn$_{2}$S$_{2}$ from the electric quadrupole (EQ) contribution. By tracking the temperature dependence of the rotation anisotropy (RA) of SHG, we capture two magnetic phase transitions, with both the SHG intensity increasing and its RA pattern rotating at $T_{C,1}$=175K and $T_{C,2}$=120K subsequently. The fitted critical exponents for the SHG intensity and RA orientation near $T_{C,1}$ and $T_{C,2}$ suggest that the magnetic phase at $T_{C,1}$ is a 3D Ising-type out-of-plane ferromagnetism while the other at $T_{C,2}$ is a 3D XY-type all-in-all-out in-plane antiferromagnetism. Our results show the success of detection and exploration of EQ SHG in a centrosymmetric magnetic WSM, and hence open the pathway towards the future investigation of its tie to the band topology.

The three way Dirac operator and dynamical Turing and Dirac induced patterns on nodes and links. (arXiv:2310.15538v1 [nlin.PS])
Riccardo Muolo, Timoteo Carletti, Ginestra Bianconi

Topological signals are dynamical variables not only defined on nodes but also on links of a network that are gaining significant attention in non-linear dynamics and topology and have important applications in brain dynamics. Here we show that topological signals on nodes and links of a network can generate dynamical patterns when coupled together. In particular, dynamical patterns require at least three topological signals, here taken to be two node signals and one link signal. In order to couple these signals, we formulate the 3-way topological Dirac operator that generalizes previous definitions of the 2-way and 4-way topological Dirac operators. We characterize the spectral properties of the 3-way Dirac operator and we investigate the dynamical properties of the resulting Turing and Dirac induced patterns. Here we emphasize the distinct dynamical properties of the Dirac induced patterns which involve topological signals only coupled by the 3-way topological Dirac operator in absence of the Hodge-Laplacian coupling. While the observed Turing patterns generalize the Turing patterns typically investigated on networks, the Dirac induced patterns have no equivalence within the framework of node based Turing patterns. These results open new scenarios in the study of Turing patterns with possible application to neuroscience and more generally to the study of emergent patterns in complex systems.

Phase chimera states on non-local hyperrings. (arXiv:2310.15540v1 [nlin.PS])
Riccardo Muolo, Thierry Njougouo, Lucia Valentina Gambuzza, Timoteo Carletti, Mattia Frasca

Chimera states are dynamical states where regions of synchronous trajectories coexist with incoherent ones. A significant amount of research has been devoted to study chimera states in systems of identical oscillators, non-locally coupled through pairwise interactions. Nevertheless, there is an increasing evidence, also supported by available data, that complex systems are composed by multiple units experiencing many-body interactions, that can be modeled by using higher-order structures beyond the paradigm of classic pairwise networks. In this work we investigate whether phase chimera states appear in this framework, by focusing on a novel topology solely involving many-body, non-local and non-regular interactions, hereby named non-local d-hyperring, being (d+1) the order of the interactions. We present the theory by using the paradigmatic Stuart-Landau oscillators as node dynamics, and show that phase chimera states emerge in a variety of structures and with different coupling functions. For comparison, we show that, when higher-order interactions are "flattened" to pairwise ones, the chimera behavior is weaker and more elusive.

Quantum geometry encoded to pair potentials. (arXiv:2310.15558v1 [cond-mat.supr-con])
Akito Daido, Taisei Kitamura, Youichi Yanase

Bloch wave functions of electrons have properties called quantum geometry, which has recently attracted much attention as the origin of intriguing physical phenomena. In this paper, we introduce the notion of the quantum-geometric pair potentials (QGPP) based on the generalized band representation and thereby clarify how the quantum geometry of electrons is transferred to the Cooper pairs they form. QGPP quantifies the deviation of multiband superconductors from an assembly of single-band superconductors and has a direct connection to the quantum-geometric corrections to thermodynamic coefficients. We also discuss their potential ability to emulate exotic pair potentials and engineer intriguing superconducting phenomena including topological superconductivity.

Linear magneto-conductivity as a DC probe of time-reversal symmetry breaking. (arXiv:2310.15631v1 [cond-mat.mes-hall])
Veronika Sunko, Chunxiao Liu, Marc Vila, Ilyoun Na, Yuchen Tang, Vladyslav Kozii, Sinéad M. Griffin, Joel E. Moore, Joseph Orenstein

Several optical experiments have shown that in magnetic materials the principal axes of response tensors can rotate in a magnetic field. Here we offer a microscopic explanation of this effect, and propose a closely related DC transport phenomenon -- an off-diagonal \emph{symmetric} conductivity linear in a magnetic field, which we refer to as linear magneto-conductivity (LMC). Although LMC has the same functional dependence on magnetic field as the Hall effect, its origin is fundamentally different: LMC requires time-reversal symmetry to be broken even before a magnetic field is applied, and is therefore a sensitive probe of magnetism. We demonstrate LMC in three different ways: via a tight-binding toy model, density functional theory calculations on MnPSe$_3$, and a semiclassical calculation. The third approach additionally identifies two distinct mechanisms yielding LMC: momentum-dependent band magnetization and Berry curvature. Finally, we propose an experimental geometry suitable for detecting LMC, and demonstrate its applicability using Landauer-B\"{u}ttiker simulations. Our results emphasize the importance of measuring the full conductivity tensor in magnetic materials, and introduce LMC as a new transport probe of symmetry.

Tuning the topological character of half-Heusler systems: A comparative study on Y$T$Bi ($T$ = Pd, Pt). (arXiv:2310.15708v1 [cond-mat.mtrl-sci])
J. C. Souza, M. V. Ale Crivillero, H. Dawczak-Dębicki, Andrzej Ptok, P. G. Pagliuso, S. Wirth

Half-Heusler systems host a plethora of different ground states, especially with non-trivial topology. However, there is still a lack of spectroscopic insight into the corresponding band inversion in this family. In this work, we locally explore the half-Heuslers Y$T$Bi ($T =$ Pt and Pd) by means of scanning tunneling microscopy/spectroscopy. From our analysis of the (120) surface plane, we infer that the increase of the spin--orbit coupling upon going from Pd to Pt is the main player in tuning the surface states from trivial to topologically non-trivial. Our measurements unveil a ($2 \times 1$) reconstruction of the (120) surface of both systems. Using density functional theory calculations, we show that the observed different behavior of the local density of states near the Fermi level in these two materials is directly related to the presence of metallic surface states. Our work sheds new light on a well known tunable family of materials and opens new routes to explore the presence of topological states of matter in half-Heusler systems and its microscopic observation.

Local Chern Marker for Periodic Systems. (arXiv:2310.15783v1 [cond-mat.mes-hall])
Nicolas Baù, Antimo Marrazzo

Topological invariants are global properties of the ground-state wave function, typically defined as winding numbers in reciprocal space. Over the years, a number of topological markers in real space have been introduced, allowing to map topological order in heterogeneous crystalline and disordered systems. Notably, even if these formulations can be expressed in terms of lattice-periodic quantities, they can actually be deployed in open boundary conditions only, as in practice they require computing the position operator $\mathbf{r}$ which is ill-defined in periodic boundary conditions. Here we derive a local Chern marker for infinite two-dimensional systems with periodic boundary conditions in the large supercell limit, where the electronic structure is sampled with one single point in reciprocal space. We validate our approach with tight-binding numerical simulations on the Haldane model, including trivial/topological superlattices made of pristine and disordered Chern insulators. The strategy introduced here is very general and could be applied to other topological invariants and geometrical quantities in any dimension.

Elementary excitations in the hybrid Bose-Fermi system induced by circularly polarized light in a two-dimensional gas of charge carriers with different masses. (arXiv:2310.15864v1 [cond-mat.mes-hall])
V. M. Kovalev, M. V. Boev, O. V. Kibis

We developed a theory describing elementary excitations in the Bose-Fermi system induced by circularly polarized light in a two-dimensional (2D) gas of charge carriers with different masses. In such a hybrid system, the Fermi subsystem is a degenerate Fermi gas, whereas the Bose subsystem is a condensate of the light-induced composite bosons consisting of two fermions (electrons or holes) with different effective masses. The interaction of the single-particle excitations and the collective excitations (plasmons) in the Fermi subsystem with the Bogoliubov collective modes (bogolons) in the Bose subsystem is analyzed. The renormalization and damping (lifetime) of the excitations are calculated, and the possibility of their experimental observation is discussed. The developed theory can be applied to describe 2D condensed-matter structures containing charge carriers with different effective masses, including transition metal dichalcogenide monolayers and semiconductor quantum wells.

Theory of correlated Chern insulators in twisted bilayer graphene. (arXiv:2310.15982v1 [cond-mat.mes-hall])
Xiaoyu Wang, Oskar Vafek

Magic-angle twisted bilayer graphene is the best studied physical platform featuring moire potential induced narrow bands with non-trivial topology and strong electronic correlations. Despite their significance, the Chern insulating states observed at a finite magnetic field -- and extrapolating to a band filling, $s$, at zero field -- remain poorly understood. Unraveling their nature is among the most important open problems in the province of moir\'e materials. Here we present the first comprehensive study of interacting electrons in finite magnetic field while varying the electron density, twist angle and heterostrain. Within a panoply of correlated Chern phases emerging at a range of twist angles, we uncover a unified description for the ubiquitous sequence of states with the Chern number $t$ for $(s,t)=\pm (0,4), \pm(1,3),\pm(2,2)$ and $\pm(3,1)$. We also find correlated Chern insulators at unconventional sequences with $s+t\neq \pm 4$, as well as with fractional $s$, and elucidate their nature.

Holographic $a$-functions and Boomerang RG Flows. (arXiv:2310.15983v1 [hep-th])
Elena Cáceres, Rodrigo Castillo Vásquez, Karl Landsteiner, Ignacio Salazar Landea

We use the radial null energy condition to construct a monotonic $a$-function for a certain type of non-relativistic holographic RG flows. We test our $a$-function in three different geometries that feature a Boomerang RG flow, characterized by a domain wall between two AdS spaces with the same AdS radius, but with different (and sometimes directions dependent) speeds of light. We find that the $a$-function monotonically decreases and goes to a constant in the asymptotic regimes of the geometry. Using the holographic dictionary in this asymptotic AdS spaces, we find that the $a$-function not only reads the fixed point central charge but also the speed of light, suggesting what the correct RG charge might be for non-relativistic RG flows.

Symmetry-breaking pathway towards the unpinned broken helix. (arXiv:2310.16018v1 [cond-mat.str-el])
E. Donoway, T. V. Trevisan, A. Liebman - Peláez, R. P. Day, K. Yamakawa, Y. Sun, J. R. Soh, D. Prabhakaran, A. Boothroyd, R. M. Fernandes, J. G. Analytis, J. E. Moore, J. Orenstein, V. Sunko

One of the prime material candidates to host the axion insulator state is EuIn$_{2}$As$_{2}$. First-principles calculations predicted the emergence of this exotic topological phase based on the assumption of a collinear antiferromagnetic structure. However, neutron scattering measurements revealed a more intricate magnetic ground state, characterized by two coexisting magnetic wavevectors, reached by successive thermal phase transitions. The proposed high and low temperature phases were a spin helix and a state with interpenetrating helical and antiferromagnetic order, termed a broken helix, respectively. Despite its complexity, the broken helix still protects the axion state because the product of time-reversal and a rotational symmetry is preserved. Here we identify the magnetic structure associated with these two phases using a multimodal approach that combines symmetry-sensitive optical probes, scattering, and group theoretical analysis. We find that the higher temperature phase hosts a nodal structure rather than a helix, characterized by a variation of the magnetic moment amplitude from layer to layer, with the moment vanishing entirely in every third Eu layer. The lower temperature structure is similar to the broken helix, with one important difference: the relative orientation of the magnetic structure and the lattice is not fixed, resulting in an `unpinned broken helix'. As a result of the breaking of rotational symmetry, the axion phase is not generically protected. Nevertheless, we show that it can be restored if the magnetic structure is tuned with externally-applied uniaxial strain. Finally, we present a spin Hamiltonian that identifies the spin interactions needed to account for the complex magnetic order in EuIn$_{2}$As$_{2}$. Our work highlights the importance of the multimodal approach in determining the symmetry of complex order-parameters.

Fate of density waves in the presence of a higher order van Hove singularity. (arXiv:2205.08828v2 [cond-mat.str-el] UPDATED)
Alkistis Zervou, Dmitriy V. Efremov, Joseph J. Betouras

Topological transitions in electronic band structures, resulting in van Hove singularities in the density of states, can considerably affect various types of orderings in quantum materials. Regular topological transitions (of neck formation or collapse) lead to a logarithmic divergence of the electronic density of states (DOS) as a function of energy in two-dimensions. In addition to the regular van Hove singularities, there are higher order van Hove singularities (HOVHS) with a power-law divergences in DOS. By employing renormalization group (RG) techniques, we study the fate of a spin-density wave phase formed by nested parts of the Fermi surface, when a HOVHS appears in parallel. We find that the phase formation can be boosted by the presence of the singularity, with the critical temperature increasing by orders of magnitude. We discuss possible applications of our findings to a range of quantum materials such as Sr$_3$Ru$_2$O$_7$, Sr$_2$RuO$_4$ and transition metal dichalcogenides.

Finite-time Landauer principle beyond weak coupling. (arXiv:2211.02065v3 [quant-ph] UPDATED)
Alberto Rolandi, Martí Perarnau-Llobet

Landauer's principle gives a fundamental limit to the thermodynamic cost of erasing information. Its saturation requires a reversible isothermal process, and hence infinite time. We develop a finite-time version of Landauer's principle for a bit encoded in the occupation of a single fermionic mode, which can be strongly coupled to a reservoir. By solving the exact non-equilibrium dynamics, we optimize erasure processes (taking both the fermion's energy and system-bath coupling as control parameters) in the slow driving regime through a geometric approach to thermodynamics. We find analytic expressions for the thermodynamic metric and geodesic equations, which can be solved numerically. Their solution yields optimal processes that allow us to characterize a finite-time correction to Landauer's bound, fully taking into account non-markovian and strong coupling effects.

Transport in honeycomb lattice with random $\pi$-fluxes: implications for low-temperature thermal transport in the Kitaev spin liquids. (arXiv:2211.16719v4 [cond-mat.mes-hall] UPDATED)
Zekun Zhuang

Motivated by the thermal transport problem in the Kitaev spin liquids, we consider a nearest-neighbor tight-binding model on the honeycomb lattice in the presence of random uncorrelated $\pi$-fluxes. We employ different numerical methods to study its transport properties near half-filling. The zero-temperature DC conductivity away from the Dirac point is found to be quadratic in Fermi momentum and inversely proportional to the flux density. Localization due to the random $\pi$-fluxes is observed and the localization length is extracted. Our results imply that, for realistic system size, the thermal conductivity of a pure Kitaev spin liquid diverges as $\kappa_\text{K}\sim T^3 e^{\Delta_v/k_BT}$ when $k_B T\ll \Delta_v$, and suggest the possible occurrence of strong Majorana localization $\kappa_\text{K}/T\ll k_B^2/2\pi\hbar$ when $k_B T\sim \Delta_v$, where $\Delta_v$ is the vison gap.

Effects of Co substitution on the structural and magnetic properties of Sr(Ni$_{1-x}$Co$_x$)$_2$P$_2$. (arXiv:2305.01805v2 [cond-mat.str-el] UPDATED)
Juan Schmidt, Guilherme Gorgen-Lesseux, Raquel A. Ribeiro, Sergey L. Bud'ko, Paul C. Canfield

Although SrNi$_2$P$_2$ adopts the common ThCr$_2$Si$_2$ structure for $T\geq 325$ K, being in an uncollapsed tetragonal (ucT) state, on cooling below 325 K it adopts a one-third collapsed orthorhombic (tcO) phase where one out of every three P-rows bond across the Sr layers. On the other hand, SrCo$_2$P$_2$ only exhibits the uncollapsed ThCr$_2$Si$_2$ structure from room temperature down to 1.8 K. Neither SrNi$_2$P$_2$ nor SrCo$_2$P$_2$ manifest magnetic transitions down to 50 mK and 2 K, respectively. In this work we report the effects of Co substitution in Sr(Ni$_{1-x}$Co$_x$)$_2$P$_2$, which allows for tuning the transition between the one-third collapsed and the uncollapsed structure. We find a rapid decrease of the one-third collapsed structural transition temperature with increasing Co fraction, until reaching full suppression for $x \geq 0.1$. Substitution levels in the range $0.11\leq x\leq 0.58$ show no signs of any transition down to 1.8 K in the magnetization or resistance measurements in the range $1.8\ \text{K}\leq T\leq 300\ \text{K}$. However, different magnetically ordered states emerge for $x\geq 0.65$, and disappear for $x\geq 0.99$, recovering the known paramagnetic properties of the parent compound SrCo$_2$P$_2$. These results are summarized in a phase diagram, built upon the characterization done on single crystals with different Co fraction. Both the magnetic and structural properties are compared to other systems with ThCr$_2$Si$_2$ structure that exhibit magnetic ordering and collapsed tetragonal transitions. The magnetic ordering and moment formation are well described by Takahashi's spin fluctuation theory of itinerant electron magnetism.

Fundamental bound on topological gap. (arXiv:2306.00078v3 [cond-mat.mes-hall] UPDATED)
Yugo Onishi, Liang Fu

We provide a universal tight bound on the energy gap of topological insulators by exploring relationships between topology, quantum geometry, and optical absorption. Applications of our theory to infrared absorption near topological band inversion, magnetic circular dichorism in Chern insulators, and topological gap in moir\'e materials are demonstrated.

Zero-field composite Fermi liquid in twisted semiconductor bilayers. (arXiv:2306.02513v2 [cond-mat.mes-hall] UPDATED)
Hart Goldman, Aidan P. Reddy, Nisarga Paul, Liang Fu

Recent experiments have produced evidence for fractional quantum anomalous Hall (FQAH) states at zero magnetic field in the semiconductor moir\'e superlattice system $t$MoTe$_2$. Here we argue that a composite fermion description, already a unifying framework for the phenomenology of 2d electron gases at high magnetic fields, provides a similarly powerful perspective in this new context. To this end, we present exact diagonalization evidence for composite Fermi liquid states at zero magnetic field in $t$MoTe$_2$ at fillings $n=\frac{1}{2}$ and $n=\frac{3}{4}$. We dub these non-Fermi liquid metals anomalous composite Fermi liquids (ACFLs), and we argue that they play a central organizing role in the FQAH phase diagram. We proceed to develop a long wavelength theory for this ACFL state that offers concrete experimental predictions upon doping the composite Fermi sea, including a Jain sequence of FQAH states and a new type of commensurability oscillations originating from the superlattice potential intrinsic to the system.

Visualizing the melting of the charge density wave in UTe2 by generation of pairs of topological defects with opposite winding. (arXiv:2306.09423v2 [cond-mat.supr-con] UPDATED)
Anuva Aishwarya, Julian May-Mann, Avior Almoalem, Sheng Ran, Shanta R. Saha, Johnpierre Paglione, Nicholas P. Butch, Eduardo Fradkin, Vidya Madhavan

Topological defects are singularities in an ordered phase that can have a profound effect on phase transitions and serve as a window into the order parameter. In this work we use scanning tunneling microscopy to visualize the role of topological defects in the novel magnetic field induced disappearance of an intertwined charge density wave (CDW) in the heavy fermion superconductor, UTe2. By simultaneously imaging the amplitude and phase of the CDW order, we reveal pairs of topological defects with positive and negative phase winding. The pairs are directly correlated with a zero CDW amplitude and increase in number with increasing magnetic field. These observations can be captured by a Ginzburg Landau model of a uniform superconductor coexisting with a pair density wave. A magnetic field generates vortices of the superconducting and pair density wave order which can create topological defects in the CDW and induce the experimentally observed melting of the CDW at the upper critical field. Our work reveals the important role of magnetic field generated topological defects in the melting the CDW order parameter in UTe2 and provides support for the existence of a parent pair density wave order on the surface of UTe2.

Fractonic Higher-Order Topological Phases in Open Quantum Systems. (arXiv:2307.05474v2 [cond-mat.str-el] UPDATED)
Jian-Hao Zhang, Ke Ding, Shuo Yang, Zhen Bi

In this work, we study the generalization of decohered average symmetry-protected topological phases to open quantum systems with a combination of subsystem symmetries and global symmetries. In particular, we provide examples of two types of intrinsic average higher-order topological phases with average subsystem symmetries. A classification scheme for these phases based on generalized anomaly cancellation criteria of average symmetry is also discussed.

Superconductivity from incoherent Cooper pairs in strong-coupling regime. (arXiv:2308.04508v3 [cond-mat.supr-con] UPDATED)
Alexander A. Zyuzin, A. Yu. Zyuzin

We propose a scenario for superconductivity at strong electron-electron attractive interaction, in the situation when the increase of interaction strength promotes the nucleation of the local Cooper pairs and forms a state with a spatially phase incoherent Cooper pair order parameter. We show that this state can be characterized by a pseudogap and a scattering rate, which are determined by the self-energy due to electron scattering on phase fluctuations. At low temperatures, however, long-range correlations between the regions with different phases become important and establish global phase coherence hence superconductivity in the system. We develop a mean-field theory to describe a phase transition between the preformed Cooper pair and superconducting states. The superconducting transition temperature and the upper critical magnetic field are shown to be enhanced in the strong coupling case. The mean-field approach is justified by the small value of the Ginzburg-Levanyuk parameter. This scenario of superconductivity applies not only to conductors with parabolic bands but also to the flat-band systems in which flat and dispersive bands coexist and responsible for the Cooper pairs formation as well as their phase synchronization.

Universal and nonuniversal probability laws in Markovian open quantum dynamics subject to generalized reset processes. (arXiv:2310.06981v2 [cond-mat.stat-mech] UPDATED)
Federico Carollo, Igor Lesanovsky, Juan P. Garrahan

We consider quantum jump trajectories of Markovian open quantum systems subject to stochastic in time resets of their state to an initial configuration. The reset events provide a partitioning of quantum trajectories into consecutive time intervals, defining sequences of random variables from the values of a trajectory observable within each of the intervals. For observables related to functions of the quantum state, we show that the probability of certain orderings in the sequences obeys a universal law. This law does not depend on the chosen observable and, in case of Poissonian reset processes, not even on the details of the dynamics. When considering (discrete) observables associated with the counting of quantum jumps, the probabilities in general lose their universal character. Universality is only recovered in cases when the probability of observing equal outcomes in a same sequence is vanishingly small, which we can achieve in a weak reset rate limit. Our results extend previous findings on classical stochastic processes [N.~R.~Smith et al., EPL {\bf 142}, 51002 (2023)] to the quantum domain and to state-dependent reset processes, shedding light on relevant aspects for the emergence of universal probability laws.

Direct observation and control of near-field radiative energy transfer in a natural hyperbolic material. (arXiv:2310.08351v2 [cond-mat.mes-hall] UPDATED)
L. Abou-Hamdan, A. Schmitt, R. Bretel, S. Rossetti, M. Tharrault, D. Mele, A. Pierret, M. Rosticher, T. Taniguchi, K. Watanabe, C. Maestre, C. Journet, B. Toury, V. Garnier, P. Steyer, J. H. Edgar, E. Janzen, J-M. Berroir, G. Fève, G. Ménard, B. Plaçais, C. Voisin, J-P. Hugonin, E. Bailly, B. Vest, J-J. Greffet, P. Bouchon, Y. De Wilde, E. Baudin

Heat control is a key issue in nano-electronics, where new efficient energy transfer mechanisms are highly sought after. In this respect, there is indirect evidence that high-mobility hexagonal boron nitride (hBN)-encapsulated graphene exhibits hyperbolic out-of-plane radiative energy transfer when driven out-of-equilibrium. Here we directly observe radiative energy transfer due to the hyperbolic phonon polaritons modes of the hBN encapsulant in intrinsic graphene devices under large bias, using mid-infrared spectroscopy and pyrometry. By using different hBN crystals of varied crystalline quality, we engineer the energy transfer efficiency, a key asset for compact thermal management of electronic circuits.

Bulk-edge correspondence for nonlinear eigenvalue problems. (arXiv:2310.12577v2 [cond-mat.mes-hall] UPDATED)
Takuma Isobe, Tsuneya Yoshida, Yasuhiro Hatsugai

Although topological phenomena attract growing interest not only in linear systems but also in nonlinear systems, the bulk-edge correspondence under the nonlinearity of eigenvalues has not been established so far. We address this issue by introducing auxiliary eigenvalues. We reveal that the topological edge states of auxiliary eigenstates are topologically inherited as physical edge states when the nonlinearity is weak but finite (i.e., auxiliary eigenvalues are monotonic as for the physical one). This result leads to the bulk-edge correspondence with the nonlinearity of eigenvalues.

Found 7 papers in prb
Date of feed: Wed, 25 Oct 2023 03:17:01 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)

Resonant x-ray diffraction study using circularly polarized x rays on antiferromagnetic ${\mathrm{TbB}}_{4}$
R. Misawa, K. Arakawa, T. Yoshioka, H. Ueda, F. Iga, K. Tamasaku, Y. Tanaka, and T. Kimura
Author(s): R. Misawa, K. Arakawa, T. Yoshioka, H. Ueda, F. Iga, K. Tamasaku, Y. Tanaka, and T. Kimura

The interference effect between the magnetic scattering and the charge scattering in resonant x-ray diffraction (RXD) leads to circular dichroism. The authors utilize this effect here to distinguish the antiferromagnetic (AFM) domain state in the noncollinear antiferromagnet TbB4, breaking both the space-inversion (P) and time-reversal (T) symmetries but preserving the combined PT symmetry. This result shows that circularly polarized RXD using the interference effect enables us to detect AFM order parameters and spatially resolve the domain state in PT-symmetric AFM materials.

[Phys. Rev. B 108, 134433] Published Tue Oct 24, 2023

Perfect crossed Andreev reflection in the proximitized graphene/superconductor/proximitized graphene junctions
Shu-Chang Zhao, Lu Gao, Qiang Cheng, and Qing-Feng Sun
Author(s): Shu-Chang Zhao, Lu Gao, Qiang Cheng, and Qing-Feng Sun

We study the crossed Andreev reflection and the nonlocal transport in the proximitized graphene/ superconductor/proximitized graphene junctions with the pseudospin staggered potential and the intrinsic spin-orbit coupling. The crossed Andreev reflection with the local Andreev reflection and the elas…

[Phys. Rev. B 108, 134511] Published Tue Oct 24, 2023

Topological states of ${\mathrm{Sr}}_{3}\mathrm{PbO}$: From topological crystalline insulator phase in the bulk to quantum spin Hall insulator phase in the thin-film limit
Hei Lam, Rui Peng, Ziyu Wang, Chunyu Wan, and Junwei Liu
Author(s): Hei Lam, Rui Peng, Ziyu Wang, Chunyu Wan, and Junwei Liu

Nontrivial topological materials are emerging as fascinating objects in condensed matter research due to their great potential in low-power and low-dissipation electronic applications. In this work, using first-principles calculations and a tight-binding method, we propose a promising candidate with…

[Phys. Rev. B 108, 155139] Published Tue Oct 24, 2023

Realizing Majorana Kramers pairs in two-channel InAs-Al nanowires with highly misaligned electric fields
Benjamin D. Woods and Mark Friesen
Author(s): Benjamin D. Woods and Mark Friesen

Common proposals for realizing topological superconductivity and Majorana zero modes in semiconductor-superconductor hybrids require large magnetic fields, which paradoxically suppress the superconducting gap of the parent superconductor. Although two-channel schemes have been proposed as a way to e…

[Phys. Rev. B 108, 155142] Published Tue Oct 24, 2023

Temperature-dependent collective excitations in the three-dimensional Dirac system ${\mathrm{ZrTe}}_{5}$
Zijian Lin, Cuixiang Wang, Daqiang Chen, Sheng Meng, Youguo Shi, Jiandong Guo, and Xuetao Zhu
Author(s): Zijian Lin, Cuixiang Wang, Daqiang Chen, Sheng Meng, Youguo Shi, Jiandong Guo, and Xuetao Zhu

Zirconium pentatelluride $({\mathrm{ZrTe}}_{5})$, a system with a Dirac linear band across the Fermi level and anomalous transport features, has attracted considerable research interest for it is predicted to be located at the boundary between strong and weak topological insulators separated by a to…

[Phys. Rev. B 108, 165146] Published Tue Oct 24, 2023

Majorana bound states in a $d$-wave superconductor planar Josephson junction
Hamed Vakili, Moaz Ali, Mohamed Elekhtiar, and Alexey A. Kovalev
Author(s): Hamed Vakili, Moaz Ali, Mohamed Elekhtiar, and Alexey A. Kovalev

We study phase-controlled planar Josephson junctions comprising a two-dimensional electron gas with strong spin-orbit coupling and $d$-wave superconductors, which have an advantage of a high critical temperature. We show that a region between the two superconductors can be tuned into a topological s…

[Phys. Rev. B 108, L140506] Published Tue Oct 24, 2023

Tuning corner states in proximitized second-order topological insulators with bulk-boundary obstruction
Yang Xue, Tong Zhou, Wei Xu, Bao Zhao, Igor Žutić, and Zhongqin Yang
Author(s): Yang Xue, Tong Zhou, Wei Xu, Bao Zhao, Igor Žutić, and Zhongqin Yang

Second-order topological insulators (SOTIs) support topological states beyond the usual bulk-boundary correspondence and provide important connections between quantum chemistry and topology. A hallmark of the two-dimensional (2D) SOTIs is the emergence of corner states, which usually arise from the …

[Phys. Rev. B 108, L161110] Published Tue Oct 24, 2023

Found 1 papers in prl
Date of feed: Wed, 25 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)

Many-Body Majorana Braiding without an Exponential Hilbert Space
Eric Mascot, Themba Hodge, Dan Crawford, Jasmin Bedow, Dirk K. Morr, and Stephan Rachel
Author(s): Eric Mascot, Themba Hodge, Dan Crawford, Jasmin Bedow, Dirk K. Morr, and Stephan Rachel

Qubits built out of Majorana zero modes constitute the primary path toward topologically protected quantum computing. Simulating the braiding process of multiple Majorana zero modes corresponds to the quantum dynamics of a superconducting many-body system. It is crucial to study the Majorana dynamic…

[Phys. Rev. Lett. 131, 176601] Published Tue Oct 24, 2023

Found 1 papers in pr_res
Date of feed: Wed, 25 Oct 2023 03:17:01 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)

Magic angle butterfly in twisted trilayer graphene
Fedor K. Popov and Grigory Tarnopolsky
Author(s): Fedor K. Popov and Grigory Tarnopolsky

We consider a configuration of three stacked graphene monolayers with commensurate twist angles ${θ}_{12}/{θ}_{23}=p/q$, 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…

[Phys. Rev. Research 5, 043079] Published Tue Oct 24, 2023

Found 1 papers in nano-lett
Date of feed: Tue, 24 Oct 2023 13:08:27 GMT

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

[ASAP] Quantum Phase Transition in Magnetic Nanographenes on a Lead Superconductor
Yu Liu, Can Li, Fu-Hua Xue, Wei Su, Ying Wang, Haili Huang, Hao Yang, Jiayi Chen, Dandan Guan, Yaoyi Li, Hao Zheng, Canhua Liu, Mingpu Qin, Xiaoqun Wang, Rui Wang, Deng-Yuan Li, Pei-Nian Liu, Shiyong Wang, and Jinfeng Jia

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Nano Letters
DOI: 10.1021/acs.nanolett.3c02208

Found 1 papers in acs-nano
Date of feed: Tue, 24 Oct 2023 13:04:42 GMT

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

[ASAP] Emerging Nontrivial Topology in Ultrathin Films of Rare-Earth Pnictides
Dai Q. Ho, Ruiqi Hu, D. Quang To, Garnett W. Bryant, and Anderson Janotti

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ACS Nano
DOI: 10.1021/acsnano.3c03307

Found 2 papers in scipost

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

Boundary states of Three Dimensional Topological Order and the Deconfined Quantum Critical Point, by Wenjie Ji, Nathanan Tantivasadakarn, Cenke Xu
< author missing >
Submitted on 2023-10-24, refereeing deadline 2023-11-08.

Topological semimetals with antiferromagnetic order in Hubbard model, by Garima Goyal, Dheeraj Kumar Singh
< author missing >
Submitted on 2023-10-24, refereeing deadline 2023-11-07.