Found 37 papers in cond-mat

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Altermagnetism from coincident Van Hove singularities: application to $\kappa$-Cl
Yue Yu Han-Gyeol Suh Merc\`e Roig Daniel F. Agterberg
Realizing two-dimensional (2D) altermagnets is important for spintronics applications. Here we propose a microscopic template for stabilizing 2D altermagnetism through Van Hove singularities that are coincident in both energy and momentum. These coincident Van Hove singularities are a generic consequence of non-symmorphic symmetries in 8 2D space groups. They allow new hopping interactions between the Van Hove singularities that do not appear in analogous Van-Hove singularity based patch models for cuprates and graphene. We show these new interactions can give rise to various weak coupling, and BCS-based instabilities, including altermagnetism, nematicity, inter-band d-wave superconductivity, and orbital altermagnetic order. We apply our results to quasi-2D organic $\kappa$-Cl in which altermagnetism is known to appear.

Classical and Quantum Theory of Fluctuations for Many-Particle Systems out of Equilibrium
Erik Schroedter Michael Bonitz
Correlated classical and quantum many-particle systems out of equilibrium are of high interest in many fields, including dense plasmas, correlated solids, and ultracold atoms. Accurate theoretical description of these systems is challenging both, conceptionally and with respect to computational resources. While for classical systems, in principle, exact simulations are possible via molecular dynamics, this is not the case for quantum systems. Alternatively, one can use many-particle approaches such as hydrodynamics, kinetic theory or nonequilibrium Green functions (NEGF). However, NEGF exhibit a very unfavorable cubic scaling of the CPU time with the number of time steps. An alternative is the G1--G2 scheme [N. Schl\"unzen et al., Phys. Rev. Lett. \textbf{124}, 076601 (2020)] which allows for NEGF simulations with time linear scaling, however, at the cost of large memory consumption. The reason is the need to store the two-particle correlation function. This problem can be overcome for a number of approximations by reformulating the kinetic equations in terms of fluctuations -- an approach that was developed, for classical systems, by Yu.L. Klimontovich [JETP \textbf{33}, 982 (1957)]. Here we present an overview of his ideas and extend them to quantum systems. In particular, we demonstrate that this quantum fluctuations approach can reproduce the nonequilibrium $GW$ approximation [E. Schroedter \textit{et al.}, Cond. Matt. Phys. \textbf{25}, 23401 (2022)] promising high accuracy at low computational cost which arises from an effective semiclassical stochastic sampling procedure. We also demonstrate how to extend the approach to the two-time exchange-correlation functions and the density response properties. [E. Schroedter \textit{et al.}, Phys. Rev. B \textbf{108}, 205109 (2023)].

Controlling the orbital Hall effect in gapped bilayer graphene in the terahertz regime
Tarik P. Cysne W. J. M. Kort-Kamp Tatiana G. Rappoport
We study the orbital Hall effect (OHE) in the AC regime using bilayer graphene (BLG) as a prototypical material platform. While the unbiased BLG has gapless electronic spectra, applying a perpendicular electric field creates an energy band gap that can be continuously tuned from zero to high values. By exploiting this flexibility, we demonstrate the ability to control the behavior of AC orbital Hall conductivity. Particularly, we demonstrate that the orbital Hall conductivity at the neutrality point changes its signal at a critical frequency, the value of which is proportional to the perpendicular electric field. For BLG with narrow band gaps, the active frequency region for the AC OHE may extend to a few terahertz, which is experimentally accessible with current technologies. We also consider the introduction of a perpendicular magnetic field in the weak coupling regime using first-order perturbation theory to illustrate how the breaking of time-reversal symmetry enables the emergence of AC charge Hall effect in the charge-doped situation and modifies the AC orbital Hall conductivity. Our calculations suggest that BLG with narrow bandgaps is a practical candidate for investigating time-dependent orbital angular momentum transport.

Impact of impurities on the topological boundaries and edge state localization in a staggered chain of atoms: SSH model and its topoelectrical circuit realization
Julio C\'esar P\'erez-Pedraza Jos\'e Eduardo Barrios-Vargas Alfredo Raya
We study the Su-Schrieffer-Hegger model, perhaps the simplest realization of a topological insulator, in the presence of an embedded impurity superlattice. We consider the impact of the said impurity by changing the hopping amplitudes between them and their nearest neighbors in the topological boundaries and the edge state localization in the chain of atoms. Within a tight-binding approach and through a topolectrical circuit simulation, we consider three different impurity-hopping amplitudes. We found a relaxation of the condition between hopping parameters for the topologically trivial and non-trivial phase boundary and a more profound edge state localization given by the impurity position within the supercell.

Prediction of $s^\pm$-wave superconductivity enhanced by electronic doping in trilayer nickelates La$_4$Ni$_3$O$_{10}$ under pressure
Yang Zhang Ling-Fang Lin Adriana Moreo Thomas A. Maier Elbio Dagotto
Motivated by the recently reported signatures of superconductivity in trilayer La$_4$Ni$_3$O$_{10}$ under pressure, we comprehensively study this system using {\it ab initio} and random-phase approximation techniques. Without electronic interactions, the Ni $d_{3z^2-r^2}$ orbitals show a bonding-antibonding and nonbonding splitting behavior via the O $p_z$ orbital inducing a ``trimer'' lattice in La$_4$Ni$_3$O$_{10}$, analogous to the dimers of La$_3$Ni$_2$O$_{7}$. The Fermi surface consists of three electron sheets with mixed $e_g$ orbitals, and a hole and an electron pocket made up of the $d_{3z^2-r^2}$ orbital, suggesting a Ni two-orbital minimum model. In addition, we find that superconducting pairing is induced in the $s_{\pm}$-wave channel due to partial nesting between the {\bf M}=$(\pi, \pi)$ centered pockets and portions of the Fermi surface centered at the {\bf $\Gamma$}=$(0, 0)$ point. With changing electronic density $n$, the $s^\pm$ instability remains leading and its pairing strength shows a dome-like behavior with a maximum around $n = 4.2$ ($\sim 6.7\%$ electron doping). The superconducting instability disappears at the same electronic density of La$_3$Ni$_2$O$_7$ correlated with the absence of the $\gamma$ pocket, suggesting that the superconductivity of La$_3$Ni$_2$O$_7$ does not originate from trilayer- and single-layer structure. Furthermore, we predict an interesting spin-density-wave state in La$_4$Ni$_3$O$_{10}$ with an in-plane ($\pi$, $\pi$) order and antiferromagnetic coupling between the top and bottom Ni layers, while the middle layer has spin zero.

3D ferroelectric phase field simulations of polycrystalline multi-phase hafnia and zirconia based ultra-thin films
Prabhat KumarJackie Michael HoffmannJackie Andrew NonakaJackie Sayeef SalahuddinJackie ZhiJackie Yao
HfO$_2$- and ZrO$_2$-based ferroelectric thin films have emerged as promising candidates for the gate oxides of next generation electronic devices. Recent work has experimentally demonstrated that a tetragonal/orthorhombic (t/o-) phase mixture with partially in-plane polarization can lead to negative capacitance (NC) stabilization. However, there is a discrepancy between experiments and the theoretical understanding of domain formation and domain wall motion in these multi-phase, polycrystalline materials. Furthermore, the effect of anisotropic domain wall coupling on NC has not been studied so far. Here we apply 3D phase field simulations of HfO$_2$- and ZrO$_2$-based mixed-phase ultra-thin films on silicon to understand the necessary and beneficial conditions for NC stabilization. We find that smaller ferroelectric grains and a larger angle of the polar axis with respect to the out-of-plane direction enhances the NC effect. Furthermore, we show that theoretically predicted negative domain wall coupling even along only one axis prevents NC stabilization. Therefore, we conclude that topological domain walls play a critical role in experimentally observed NC phenomena in HfO$_2$- and ZrO$_2$-based ferroelectrics.

Absence of breakdown of ferrodark solitons exhibiting snake instability
Xiaoquan Yu P. B. Blakie
We investigate the dynamical stability and real time dynamics of the two-types of ferrodark solitons (FDSs) which occur as topological magnetic domain walls in the easy-plane phase of a quasi-two-dimensional (2D) ferromagnetic spin-1 Bose-Einstein condensate. The type-I FDS has positive inertial mass and exhibits a single dynamical instability that generates in plane spin winding, causing polar-core spin vortex dipoles. The positive inertial mass leads to the elastic oscillations of the soliton under transverse perturbations. The type-II FDS has negative inertial mass and exhibits a snake instability and a spin-twist instability, with the latter involving the generation of out of plane spin winding. Distinct from the normal dynamics of negative mass solitons under long wave length transverse perturbations, the snake instability does not lead to the type-II FDS breaking down. Instead, segments of the type-II FDS convert to type-I and mass vortex dipoles are produced. The resulting hybridized-chain of the two soliton types and vortices exhibits complex 2D soliton dynamics at long times while the vortices remain confined and the topological structure of a magnetic domain wall is preserved.

Quantum Melting of a Disordered Wigner Solid
Ziyu Xiang Hongyuan Li Jianghan Xiao Mit H. Naik Zhehao Ge Zehao He Sudi Chen Jiahui Nie Shiyu Li Yifan Jiang Renee Sailus Rounak Banerjee Takashi Taniguchi Kenji Watanabe Sefaattin Tongay Steven G. Louie Michael F. Crommie Feng Wang
The behavior of two-dimensional electron gas (2DEG) in extreme coupling limits are reasonably well-understood, but our understanding of intermediate region remains limited. Strongly interacting electrons crystalize into a solid phase known as the Wigner crystal at very low densities, and these evolve to a Fermi liquid at high densities. At intermediate densities, however, where the Wigner crystal melts into a strongly correlated electron fluid that is poorly understood partly due to a lack of microscopic probes for delicate quantum phases. Here we report the first imaging of a disordered Wigner solid and its quantum densification and quantum melting behavior in a bilayer MoSe2 using a non-invasive scanning tunneling microscopy (STM) technique. We observe a Wigner solid with nanocrystalline domains pinned by local disorder at low hole densities. With slightly increasing electrostatic gate voltages, the holes are added quantum mechanically during the densification of the disordered Wigner solid. As the hole density is increased above a threshold (p ~ 5.7 * 10e12 (cm-2)), the Wigner solid is observed to melt locally and create a mixed phase where solid and liquid regions coexist. With increasing density, the liquid regions gradually expand and form an apparent percolation network. Local solid domains appear to be pinned and stabilized by local disorder over a range of densities. Our observations are consistent with a microemulsion picture of Wigner solid quantum melting where solid and liquid domains emerge spontaneously and solid domains are pinned by local disorder.

Investigation of double-gyroid grain boundaries beyond twinning
Jing Chen Zhangpeng Sun Kai Jiang Jie Xu
We study four double-gyroid (DG) grain boundaries (GBs) with different orientations numerically using the Landau--Brazovskii free energy, including the (422) twin boundary studied recently, a network switching GB, and two tilt GBs. Topological variations and geometric deformations are investigated. It is found that deviations in strut lengths and dihedral angles from the bulk DG substantially exceed changes in strut angles and nodal coplanarity. We also examine the spectra along the contact plane of two grains and utilize them to evaluate the GB widths. Of the four GBs we study, the network switching GB changes to the least extent topologically and geometrically, meanwhile has the lowest energy and the smallest GB width.

Magnetic field effects on the Kitaev model coupled to environment
Kiyu Fukui Yasuyuki Kato Yukitoshi Motome
Open quantum systems display unusual phenomena not seen in closed systems, such as new topological phases and unconventional phase transitions. An interesting example was studied for a quantum spin liquid in the Kitaev model [K. Yang, S. C. Morampudi, and E. J. Bergholtz, Phys. Rev. Lett. ${\bf 126}$, 077201 (2021)]; an effective non-Hermitian Kitaev model, which incorporates dissipation effects, was shown to give rise to a gapless spin liquid state with exceptional points in the Majorana dispersions. Given that an external magnetic field induces a gapped Majorana topological state in the Hermitian case, the exceptional points may bring about intriguing quantum phenomena under a magnetic field. Here we investigate the non-Hermitian Kitaev model perturbed by the magnetic field. We show that the exceptional points remain gapless up to a finite critical magnetic field, in stark contrast to the Hermitian case where an infinitesimal field opens a gap. The gapless state is stable over a wide range of the magnetic field for some particular parameter sets, and in special cases, undergoes topological transitions to another gapless state with different winding number around the exceptional points without opening a gap. In addition, in the system with edges, we find that the non-Hermitian skin effect is induced by the magnetic field, even for the parameters where the skin effect is absent at zero field. The chirality of edge states is switched through the exceptional points, similarly to the surface Fermi arcs connected by the Weyl points in three-dimensional Weyl semimetals. Our results provide a new possible route to stabilize topological gapless quantum spin liquids under the magnetic field in the presence of dissipation.

Su-Schrieffer-Heeger quasicrystal: Topology, localization, and mobility edge
D. A. Miranda T. V. C. Ant\~ao N. M. R Peres
In this paper we discussed the topological transition between trivial and nontrivial phases of a quasi-periodic (Aubry-Andr\'e like) mechanical Su-Schrieffer-Heeger (SSH) model. We find that there exists a nontrivial boundary separating the two topological phases and an analytical expression for this boundary is found. We discuss the localization of the vibrational modes using the calculation of the inverse participation ratio (IPR) and access the localization nature of the states of the system. We find three different regimes: extended, localized, and critical, depending on the intensity of the Aubry-Andr\'e spring. We further study the energy dependent mobility edge (ME) separating localized from extended eigenstates and find its analytical expression for both commensurate and incommensurate modulation wavelengths, thus enlarging the library of models possessing analytical expressions for the ME. Our results extend previous results for the theory of fermionic topological insulators and localization theory in quantum matter to the classical realm.

NMR evidence of spinon localization in kagome antiferromagnet YCu$_3$(OH)$_6$Br$_2$[Br$_{1-x}$(OH)$_x$]
Shuo Li Yi Cui Zhenyuan Zeng Yue Wang Ze Hu Jie Liu Cong Li Xiaoyu Xu Ying Chen Zhengxin Liu Shiliang Li Weiqiang Yu
We performed nuclear magnetic resonance studies on a kagome antiferromagnet YCu$_3$(OH)$_6$Br$_2$[Br$_{1-x}$(OH)$_{x}$]. No significant NMR spectral broadening is found in the Br center peak from 1 K down to 0.05 K, indicating absence of static antiferromagnetic ordering. In contrast to signatures of dominant 2D kagome antiferromagnetic fluctuations at temperature above 30 K, both the Knight shift $K_{\rm{n}}$ and the spin-lattice relaxation rate $1/T_{1}$ increase when the sample is cooled from 30 K to 8 K, which can be attributed to the scattering of spin excitations by strong non-magnetic impurities. Unusually, a hump is observed in $K_{\rm{n}}$ and $1/T_{2}$ close to 2 K (far below the exchange energy), which indicates the existence of excitations with a large density of states close to zero energy. These phenomena are reproduced by a mean-field simulation of Heisenberg model with bond-dependent exchange interactions, where the sign fluctuations in the spinon kinetic terms caused by impurities result in localization of spinons and an almost flat band close to the Fermi energy.

Exact functional integration of radial and complex slave-boson fields: thermodynamics and dynamics of the two-site extended Hubbard model
V. H. Dao R. Fr\'esard
The functional integral formulation of the Hubbard Model when treated in its Kotliar-Ruckenstein representation in the radial gauge involves fermionic, as well as complex and radial slave boson fields. In order to improve on the understanding of the interplay of the three types of fields, and on the nature of the latter, we perform a comprehensive investigation of an exactly solvable two-site cluster, as it entails all pitfalls embodied in this approach. It is first shown that the exact partition function is recovered, even when incorporating in the calculation the square root factors that are at the heart of the representation, when suitably regularized. We show that using radial slave boson fields allows to overcome all hurdles following from the normal ordering procedure. We then demonstrate that this applies to the Green's function too, as well as to the correlation functions of physical interest, thereby answering the criticisms raised by Sch\"onhammer [K. Sch\"onhammer, Phys. Rev. B \textbf{42}, 2591 (1990)]. In addition, the investigation generalizes the calculations to the Hubbard Model extended by a non-local Coulomb interaction.

The non-collinear phase of the antiferromagnetic sawtooth chain
R. Rausch C. Karrasch
The antiferromagnetic sawtooth chain is a prototypical example of a frustrated spin system with vertex-sharing triangles, giving rise to complex quantum states. Depending on the interaction parameters, this system has three phases, of which the gapless non-collinear phase (for strongly coupled basal spins and loosely attached apical spins) has received little theoretical attention so far. In this work, we comprehensively investigate the properties of the non-collinear phase using large-scale tensor network computations which exploit the full SU(2) symmetry of the underlying Heisenberg model. We study the ground state both for finite systems using the density-matrix renormalization group (DMRG) as well as for infinite chains via the variational uniform matrix-product state (VUMPS) formalism. Finite temperatures and correlation functions are tackled via imaginary- or real time evolutions, which we implement using the time-dependent variational principle (TDVP). We find that the non-collinear phase is characterized by a double-Q structure for the apex-apex correlations. Deep into the phase, two peaks merge into a single one indicating a 90-degree spiral. The apical spins are soft and highly susceptible to external perturbations; they form a large number of gapless magnetic states that are polarized by weak fields and cause a long low-temperature tail in the specific heat. The dynamic spin-structure factor exhibits additive contributions from a two-spinon continuum (excitations of the basal chain) and a gapless peak at $k=\pi/2$ (excitations of the apical spins). Small temperatures excite the gapless states and smear the spectral weight of the $k=\pi/2$ peak out into a homogeneous flat-band structure. Our results are relevant, e.g., for the material atacamite Cu$_2$Cl(OH)$_3$ in high magnetic fields.

Spectral asymmetry induces a re-entrant quantum Hall effect in a topological insulator
Li-Xian Wang Wouter Beugeling Fabian Schmitt Lukas Lunczer Julian-Benedikt Mayer Hartmut Buhmann Ewelina M. Hankiewicz Laurens W. Molenkamp
The band inversion of topological materials in three spatial dimensions is intimately connected to the parity anomaly of two-dimensional massless Dirac fermions. At finite magnetic fields, the parity anomaly reveals itself as a non-zero spectral asymmetry, i.e., a non-zero difference between the number of conduction and valence band Landau levels, due to the unpaired zero Landau level. Here, we realize this two-dimensional Dirac physics at a single surface of the three-dimensional topological insulator (Hg,Mn)Te. We observe an unconventional re-entrant quantum Hall effect that can be directly related to the occurrence of spectral asymmetry in a single topological surface state. The effect should be observable in any topological insulator where the transport is dominated by a single Dirac surface state.

Quantum Anomalous Hall Effect in $d$-Electron Kagome Systems: Chern Insulating States from Transverse Spin-Orbit Coupling
Imam Makhfudz Mikhail Cherkasskii Pierre Lombardo Steffen Sch\"afer Silvia Viola Kusminskiy Roland Hayn
Inspired by the discovery of metal-organic frameworks, the possibility of quantum anomalous Hall effect (QAHE) in two-dimensional kagome systems with $d$-orbital electrons is studied within a multi-orbital tight-binding model. In the absence of exchange-type spin-orbit coupling, isotropic Slater-Koster integrals give a band structure with relativistic (Dirac) and quadratic band crossing points at high symmetry spots in the Brillouin zone. A quantized topological invariant requires a flux-creating spin-orbit coupling, giving Chern number (per spin sector) $C=1$ not only from the familiar Dirac points at the six corners of the Brillouin zone, but also from the quadratic band crossing point at the center $\Gamma$. Surprisingly, this QAHE comes from the nontrivial effective flux induced by the transverse part of the spin-orbit coupling, exhibited by electrons in the $d$-orbital state with $m_l=0$ ($d_{z^2}$ orbital), in stark contrast to the more familiar form of QAHE due to the $d$-orbitals with $m_l \neq 0$, driven by the Ising part of spin-orbit coupling. The $C=1$ Chern plateau (per spin sector) due to Dirac point extends over a smaller region of Fermi energy than that due to quadratic band crossing. Our result hints at the promising potential of kagome metal-organic frameworks as a platform for dissipationless electronics by virtue of its unique QAHE.

Topological Kondo effect with spinful Majorana fermions
Steffen Bollmann Jukka I. V\"ayrynen Elio J. K\"onig
Motivated by the importance of studying topological superconductors beyond the mean-field approximation, we here investigate mesoscopic islands of time reversal invariant topological superconductors (TRITOPS). We characterize the spectrum in the presence of strong order parameter fluctuations in the presence of an arbitrary number of Kramers pairs of Majorana edge states and study the effect of coupling the Coulomb blockaded island to external leads. In the case of an odd fermionic parity on the island, we derive an unconventional Kondo Hamiltonian in which metallic leads couple to both topological Majorana degrees of freedom (which keep track of the parity in different leads) and the overall spin-1/2 in the island. For the simplest case of a single wire (two pairs of Majorana edge states), we demonstrate that anisotropies are irrelevant in the weak coupling renormalization group flow. This permits us to solve the Kondo problem in the vicinity of a Toulouse-like point using Abelian Bosonization. We demonstrate a residual ground state entropy of $\ln(2)$, which is protected by spin-rotation symmetry, but reduced to $\ln(\sqrt{2})$ (as in the spinless topological Kondo effect) by symmetry breaking perturbations. In the symmetric case, we further demonstrate the simultaneous presence of both Fermi liquid and non-Fermi liquid like thermodynamics (depending on the observable) and derive charge and spin transport signatures of the Coulomb blockaded island.

Carousel phase retrieval algorithm for 3D coherent X-ray diffraction imaging
Fangzhou Ai Oleg Shpyrko Vitaliy Lomakin
Coherent X-ray Diffraction Imaging (CXDI) is a unique technique that allows reconstructing 2D and 3D objects at nanoscale resolution by performing computational phase reconstruction procedures based on measured scattered intensity maps. The reconstruction procedures can have a high computational complexity and typically cannot be performed in real time during experiments. We present a carousel phase retrieval algorithm (CPRA) that represents the 3D reconstruction problem as a set of 2D reconstructions of projected images corresponding to different collected angles based on the Fourier slice theorem. To maintain the consistency between the 2D reconstructions, we introduce an iterative procedure, in which each 2D reconstruction is based on the adjacent 2D reconstructions in a periodic (carousel) manner. The use of 2D reconstructions results in major reductions of the computational time and memory consumption. We show CPRA implementation on CPU and GPU computing architectures for a test problem of a complex biological cell of various spatial sizes. CPRA exhibits speed-of 300 time on GPUs and 120 times on CPUs as compared to conventional CXDI reconstruction algorithms. CPRA also can achieve a higher reconstruction quality. The achieved speed allows for a high-resolution reconstruction of computationally large objects in real time.

Relaxation processes of densified silica glass
Antoine Cornet Valerie Martinez Dominique de Ligny Bernard Champagnon Christine Martinet
Densified SiO2 glasses, obtained from different pressure and temperature routes have been annealed over a wide range of temperature far below the glass transition temperature (500$^\circ$C-900$^\circ$C). Hot and cold compressions were useful to separate the effects of pressure and the compression temperature. In-situ micro-Raman spectroscopy was used to follow the structural evolution during the thermal relaxation. A similar glass structure between the non-densified silica and the recovered densified silica after the temperature annealing demonstrates a perfect recovery of the non-densified silica glass structure. While the density decreases monotonically, the structural relaxation takes place through a more complex mechanism, which shows that density is not a sufficient parameter to fully characterize the structure of densified silica glass. The relaxation takes place through a transitory state, consisting in an increase of the network inhomogeneity, shown by an increase in intensity of the D2 band which is associated with 3 membered rings. The activation energy of these processes is 255$\pm$45 kJ/mol for the hot compressed samples. The kinetic is overall faster for the cold compressed samples. In that last case the relaxation is partially activated by internal stresses release.

High-Performance Multi-Qubit System with Double-Transmon Couplers towards Scalable Superconducting Quantum Computers
Kentaro Kubo Yinghao Ho Hayato Goto
Tunable couplers in superconducting quantum computers have enabled fast and accurate two-qubit gates, with reported high fidelities over 0.99 in various architectures and gate implementation schemes. However, there are few tunable couplers whose performance in multi-qubit systems is clarified, except for the most widely used one: single-transmon coupler (STC). Achieving similar accuracy to isolated two-qubit systems remains challenging due to various undesirable couplings but is necessary for scalability. In this work, we numerically analyze a system of three fixed-frequency qubits coupled via two double-transmon couplers (DTCs) where nearest-neighbor qubits are highly detuned and also next nearest-neighbor ones are nearly resonant. The DTC is a recently proposed tunable coupler, which consists of two fixed-frequency transmons coupled through a common loop with an additional Josephson junction. We find that the DTC can not only reduce undesired residual couplings sufficiently, as well as in isolated two-qubits systems, but also enables implementations of 30-ns CZ gates and 10-ns $\pi/2$ pulses with fidelities of 0.9999 or higher. For comparison, we also investigate the system where the DTCs are replaced by the STCs. The results show that the DTC outperforms the STC in terms of both residual coupling suppression and gate accuracy in the above systems. From these results, we expect that the DTC architecture is promising for realizing high-performance, scalable superconducting quantum computers.

From atomic to global connectivity in the structure of the SARS-CoV2-Human ACE2 receptor complex
Varsha Subramanyan Arinnia Anto Moitrayee Bhattacharyya Smitha Vishveshwara Saraswathi Vishveshwara
We investigate connectivity properties of the SARS-CoV2 spike protein-human ACE2-receptor complex employing a protein side chain-based network method that allows us to span a range from atomic to global protein scales. We analyze network topology in terms of clusters and cliques obtained from averaging over snapshots of MD simulations (from D.E. Shaw Research). We demonstrate that SARS-CoV2 forms a more dominant, robust connection with the ACE2-receptor as compared to the less virulent SARS-CoV1. Globally, this stronger connectivity is reflected by our percolation analysis where the interface cluster for the SARS-CoV2-ACE2 complex persists when restricted to stronger and stronger bonds, as compared to the SARSCoV1- ACE2 complex. At the atomic level, interface clique structure reflects a stronger connectivity in the former complex. We pinpoint key functional residues in SARSCoV2 that play important roles in establishing this higher connectivity. Thus, our studies provide an objective method to map spatial connectivity of atomic level non-covalent interactions to global connectivity between any two amino acids in the complex. We also analyze specific snapshots of the MD simulations to highlight prominent variations in network topology that explore diverse conformational landscapes. Finally, we demonstrate that a majority of mutations that occur in the SARSCoV2 spike protein in variants of concern/interest (including the currently circulating JN.1) have been observed at the interface with the ACE2 receptor. Our analyses highlight the importance of interface interactions and provide a rationale for designing receptor-like peptides and proteins to combat immunity-escaping variants.

Wide bandgap semiconductors for radiation detection: A review
Ivana Capan
In this paper, an overview of the wide bandgap (WBG) semiconductors for radiation detection applications is presented. The recent advancements in the fabrication of high-quality wafers have enabled the remarkable WBG semiconductor device applications. The most common 4H-SiC, GaN and \b{eta}-Ga2O3 devices used for radiation detection are described. The 4H-SiC and GaN devices have already achieved exceptional results in the detection of alpha particles and neutrons, thermal neutrons in particular. While \b{eta}-Ga2O3 devices have not yet reached the same level of technological maturity (compared to 4H-SiC and GaN), their current achievements for X-ray detection indicate great potential and promising prospects for future applications.

Valley-dependent Multiple Quantum States and Topological Transitions in Germanene-based Ferromagnetic van der Waals Heterostructures
Feng Xue Jiaheng Li Yizhou Liu Ruqian Wu Yong Xu Wenhui Duan
Topological and valleytronic materials are promising for spintronic and quantum applications due to their unique properties. Using first principles calculations, we demonstrate that germanene (Ge)-based ferromagnetic heterostructures can exhibit multiple quantum states such as quantum anomalous Hall effect (QAHE) with Chern numbers of C=-1 or C=-2, quantum valley Hall effect (QVHE) with a valley Chern number of C$v$=2, valley-polarized quantum anomalous Hall effect (VP-QAHE) with two Chern numbers of C=-1 and C$v$=-1 as well as time-reversal symmetry broken quantum spin Hall effect (T-broken QSHE) with a spin Chern number of C$s$~1. Furthermore, we find that the transitions between different quantum states can occur by changing the magnetic orientation of ferromagnetic layers through applying a magnetic field. Our discovery provides new routes and novel material platforms with a unique combination of diverse properties that make it well suitable for applications in electronics, spintronics and valley electronics.

Flat-histogram algorithms: optimal parameters and extended application
Timur Shakirov
We provide analysis of the convergence properties and applicability extensions of flat-histogram algorithms, with a particular focus on the Wang-Landau algorithms (exemplified by converging stochastic approximation Monte Carlo (SAMC)) and multicanonical (MUCA) algorithms. Our investigation reveals that the optimal decay rate of the modification factor in SAMC algorithms is influenced by the number of energy bins rather than the width of the energy range. Despite the frequent naming of these algorithms based on the histogram flatness, our findings indicate that flatness demonstrates a limited correlation with estimation accuracy. We explore the implications of integrating the importance sampling technique with flat-histogram algorithms, demonstrating that this combination yields comparable or better accuracy in density of states estimations, almost independent of specific algorithmic parameters within certain bounds. Furthermore, our research extends the possibilities of the flat-histogram and importance sampling combination for investigating a range of underlying system parameters simultaneously within a single simulation. These system parameters could both originate from the potential, e.g., various relative contributions of different energy terms or characteristic interaction range, and characterize the accessible configurations, e.g., through the size of the simulation box.

Fixed width treelike neural networks capacity analysis -- generic activations
Mihailo Stojnic
We consider the capacity of \emph{treelike committee machines} (TCM) neural networks. Relying on Random Duality Theory (RDT), \cite{Stojnictcmspnncaprdt23} recently introduced a generic framework for their capacity analysis. An upgrade based on the so-called \emph{partially lifted} RDT (pl RDT) was then presented in \cite{Stojnictcmspnncapliftedrdt23}. Both lines of work focused on the networks with the most typical, \emph{sign}, activations. Here, on the other hand, we focus on networks with other, more general, types of activations and show that the frameworks of \cite{Stojnictcmspnncaprdt23,Stojnictcmspnncapliftedrdt23} are sufficiently powerful to enable handling of such scenarios as well. In addition to the standard \emph{linear} activations, we uncover that particularly convenient results can be obtained for two very commonly used activations, namely, the \emph{quadratic} and \emph{rectified linear unit (ReLU)} ones. In more concrete terms, for each of these activations, we obtain both the RDT and pl RDT based memory capacities upper bound characterization for \emph{any} given (even) number of the hidden layer neurons, $d$. In the process, we also uncover the following two, rather remarkable, facts: 1) contrary to the common wisdom, both sets of results show that the bounding capacity decreases for large $d$ (the width of the hidden layer) while converging to a constant value; and 2) the maximum bounding capacity is achieved for the networks with precisely \textbf{\emph{two}} hidden layer neurons! Moreover, the large $d$ converging values are observed to be in excellent agrement with the statistical physics replica theory based predictions.

Angular dependence of hump-shape Hall Effects for distinguishing between Karplus-Luttinger and Geometrical Origins
Z. S. Lim L. E. Chow K. H. Khoo G. J. Omar Z. Zhang Z. Luo H. Yan P. Yang R. Laskowski A. Ariando
Among various magnetic thin film heterostructures in solid state Physics, two contrasting mechanisms of the hump-shaped Hall Effects remain ambiguous and debated, namely the overlap of two opposite-signed Karplus-Luttinger Hall-loops associated with inhomogeneous collinear magnetic bubbles with perpendicular anisotropy, or the Geometrical/Topological Hall Effect associated with magnetic skyrmions. Their similarity in topology imposes difficulty in discrimination via magnetic imaging. Here, this ambiguity is overcome by the divergence exponent of angle-dependent hump peak fields via magnetic field rotation characterization on several heterostructures. Their difference in sensitivity to in-plane fields reveals that the former mechanism involves higher uniaxial anisotropy than the latter, departing from the pure skyrmion regime described by Ginzburg-Landau framework of triple-q spin-wave superposition. Various materials can be collapsed into a single curve of divergence exponent versus domain wall energy, bridging the crossover of the two aforementioned mechanisms.

Magnetotransport of single crystal Sm$_2$Ir$_2$O$_7$ across the pressure-induced quantum-critical phase boundary
M. J. Coak K. G\"otze T. Northam De La Fuente C. Castelnovo J. P. Tidey J. Singleton A. T. Boothroyd D. Prabhakaran P. A. Goddard
Rare-earth pyrochlore iridates host two interlocking magnetic sublattices of corner-sharing tetrahedra and can harbour a unique combination of frustrated moments, exotic excitations and highly correlated electrons. They are also the first systems predicted to display both topological Weyl semimetal and axion insulator phases. We have measured the transport and magnetotransport properties of single-crystal Sm$_2$Ir$_2$O$_7$ up to and beyond the pressure-induced quantum critical point for all-in-all-out (AIAO) Ir order at $p_{{\rm c}}$ = 63 kbar previously identified by resonant X-ray scattering and close to which Weyl semimetallic behavior has been previously predicted. Our findings overturn the accepted expectation that the suppression of AIAO order should lead to metallic conduction persisting down to zero temperature. Instead, the resistivity-minimum temperature, which tracks the decrease in the AIAO ordering temperature for pressures up to 30~kbar, begins to increase under further application of pressure, pointing to the presence of a second as-yet unidentified mechanism leading to non-metallic behavior. The magnetotransport does track the suppression of Ir magnetism, however, with a strong hysteresis observed only within the AIAO phase boundary, similar to that found for Ho$_2$Ir$_2$O$_7$ and attributed to plastic deformation of Ir domains. Around $p_{{\rm c}}$ we find the emergence of a new type of electronic phase, characterized by a negative magnetoresistance with small hysteresis at the lowest temperatures, and hysteresis-free positive magnetoresistance above approximately 5 K. The temperature dependence of our low-temperature transport data are found to be best described by a model consistent with a Weyl semimetal across the entire pressure range.

Understanding the vibrational density of states of liquids using instantaneous normal mode theory
Sha Jin Xue Fan Caleb Stamper Richard A. Mole Yuanxi Yu Liang Hong Dehong Yu Matteo Baggioli
Liquid dynamics play crucial roles in chemical and physical processes, ranging from biological systems to engineering applications. Yet, the vibrational properties of liquids are poorly understood when compared to the case of crystalline solids. Here, we report experimental neutron-scattering measurements of the vibrational density of states (VDOS) of water and liquid Fomblin in a wide range of temperatures. In the liquid phase, we observe a universal low-energy linear scaling of the experimental VDOS as a function of the frequency, which persists at all temperatures. The low-frequency scaling of the VDOS exhibits a sharp jump at the melting point of water, below which the standard Debye's law is recovered. On the contrary, in Fomblin, we observe a continuous transition reflecting its glassy dynamics, which is confirmed by structure measurements. More importantly, in both systems, we find that the slope of this linear behavior grows with temperature following an exponential Arrhenius-like form, as predicted by instantaneous normal mode (INM) theory. The microscopic origin of this exponential behavior lies in the thermally activated hopping across the energy barriers in the liquid potential landscape. We confirm this experimental trend using molecular dynamics simulations and show that the predictions of INM theory for the shape of the VDOS in the liquid phase are in qualitative agreement with the experimental and simulation data. On the other hand, from a more quantitative perspective, the predictions from the normal modes analysis under-estimate the energy scale entering in the exponential temperature behavior of the VDOS slope by a factor of $\approx 2$-$3$. Anharmonic effects, that are not entirely captured by the INM analysis, are probably the origin of this discrepancy.

Hydrodynamics of Quantum Vortices on a Closed Surface
Yanqi Xiong Xiaoquan Yu
We develop a neutral vortex fluid theory on closed surfaces with zero genus. The theory describes collective dynamics of many well-separated quantum vortices in a superfluid confined on a closed surface. Comparing to the case on a plane, the covariant vortex fluid equation on a curved surface contains an additional term proportional to Gaussian curvature multiplying the circulation quantum. This term describes the coupling between topological defects and curvature in the macroscopic level. For a sphere, the simplest nontrivial stationary vortex flow is obtained analytically and this flow is analogous to the celebrated zonal Rossby-Haurwitz wave in classical fluids on a nonrotating sphere. For this flow the difference between the coarse-grained vortex velocity field and the fluid velocity field generated by vortices is solely driven by curvature and vanishes in the corresponding vortex flow on a plane when the radius of the sphere goes to infinity.

Emergence of solid-like Debye scaling in the vibrational density of states of liquids under nanoconfinement
Yuanxi Yu Sha Jin Xue Fan Mona Sarter Dehong Yu Matteo Baggioli Liang Hong
At frequencies higher than the inverse of the structural relaxation time $\tau$, the dynamics of liquids display several solid-like properties, including propagating collective shear waves and emergent elasticity. However, in classical bulk liquids, where $\tau$ is typically of the order of 1 ps or less, this solid-like behavior remains elusive in the low-frequency region of the vibrational density of states (VDOS). Here, we provide compelling evidence for the emergent solid-like nature of liquids at short distances through inelastic neutron scattering measurements of the low-frequency VDOS in liquid water and glycerol confined within graphene oxide membranes. In particular, upon increasing the strength of confinement, we observe a transition from a liquid-like VDOS (linear in the frequency $\omega$) to a solid-like behavior (Debye law, $\sim\omega^2$) in the range of $1$-$4$ meV. Molecular dynamics simulations confirm these findings and reveal additional solid-like features, including propagating collective shear waves and a reduction in the self-diffusion constant. Finally, we show that the onset of solid-like dynamics is pushed towards low frequency along with the slowing-down of the relaxation processes upon confinement, and that the scale at which solidity emerges is qualitatively compatible with k-gap theory and the concept of gapped momentum states. Our results provide convincing experimental evidence of the continuity between liquids and solids, as originally advocated by Frenkel and Maxwell, and a deeper understanding of the dynamics of liquids across a wide range of length scales.

Non-Adiabatic Effect in Topological and Interacting Charge Pumping
Fan Yang Xingyu Li Hui Zhai
Topological charge pumping occurs in the adiabatic limit, and the non-adiabatic effect due to finite ramping velocity reduces the pumping efficiency and leads to deviation from quantized charge pumping. In this work, we discuss the relation between this deviation from quantized charge pumping and the entanglement generation after a pumping circle. In the simplest setting, we show that purity $\mathcal{P}$ of the half system reduced density matrix equals to $\mathcal{R}$ defined as $(1-\kappa)^2+\kappa^2$, where $\kappa$ denotes the pumping efficiency. In generic situations, we argue $\mathcal{P}<\mathcal{R}$ and the pumping efficiency can provide an upper bound for purity and, therefore, a lower bound for generated entanglement. To support this conjecture, we propose a solvable pumping scheme in the Rice--Mele--Hubbard model, which can be represented as brick-wall type quantum circuit model. With this pumping scheme, numerical calculation of charge pumping only needs to include at most six sites, and therefore, the interaction and the finite temperature effects can be both included reliably in the exact diagonalization calculation. The numerical results using the solvable pumping circle identify two regimes where the pumping efficiency is sensitive to ramping velocity and support the conjecture $\mathcal{P}<\mathcal{R}$ when both interaction and finite temperature effects are present.

Cuprate universal electronic spin response and the pseudogap from NMR
Daniel Bandur Jakob Nachtigal Abigail Lee Stefan Tsankov Juergen Haase
The understanding of high-temperature superconductivity, in particular in the cuprates, is still central to condensed matter physics, and telltale experimental laws for guiding theory are desirable. Here we report on such a universal property concerning the linear response of the electronic matter to a homogeneous static magnetic field. With the new law we can distinguish between two different spin components in all cuprates. One is the expected spin from the hybridized Cu $3d(x^2-y^2)$ and planar O $2p_\sigma$ states. It is material independent in the sense that the metallic density of states is universal, however, a temperature independent, doping dependent pseudogap causes changes of the spin polarization as a function of temperature from excitations across the gap. This pseudogap component shows a steep temperature dependence at condensation, i.e.\@ below the critical temperature, $T_\mathrm{c}$, for overdoped materials, and below the pseudogap temperature, $T^*$, at lower doping levels. A second spin component originates from symmetric (or anisotropic, \lsco), metallic Cu states that do not involve planar O significantly. The second component is family and doping dependent in the sense that the density of states increases with doping. It can condense at the same or lower temperatures as the pseudogap component, but the slope is significantly different, suggesting different pairing scenarios. Our second component reminds one of the proposed involvement of another Cu axial orbital that relates to the distance or presence of the apical oxygen [1-3] and the charge distribution in the CuO$_2$ plane [4,5], and finally the maximum $T_\mathrm{c}$.

Stacking Group Structure of Fermionic Symmetry-Protected Topological Phases
Xing-Yu Ren Shang-Qiang Ning Yang Qi Qing-Rui Wang Zheng-Cheng Gu
In the past decade, there has been a systematic investigation of symmetry-protected topological (SPT) phases in interacting fermion systems. Specifically, by utilizing the concept of equivalence classes of finite-depth fermionic symmetric local unitary (FSLU) transformations and the fluctuating decorated symmetry domain wall picture, a large class of fixed-point wave functions have been constructed for fermionic SPT (FSPT) phases. Remarkably, this construction coincides with the Atiyah-Hirzebruch spectral sequence, enabling a complete classification of FSPT phases. However, unlike bosonic SPT phases, the stacking group structure in fermion systems proves to be much more intricate. The construction of fixed-point wave functions does not explicitly provide this information. In this paper, we employ FSLU transformations to investigate the stacking group structure of FSPT phases. Specifically, we demonstrate how to compute stacking FSPT data from the input FSPT data in each layer, considering both unitary and anti-unitary symmetry, up to 2+1 dimensions. As concrete examples, we explicitly compute the stacking group structure for crystalline FSPT phases in all 17 wallpaper groups and the mixture of wallpaper groups with onsite time-reversal symmetry using the fermionic crystalline equivalence principle. Importantly, our approach can be readily extended to higher dimensions, offering a versatile method for exploring the stacking group structure of FSPT phases.

Polarization-driven band topology evolution in twisted MoTe$_2$ and WSe$_2$
Xiao-Wei Zhang Chong Wang Xiaoyu Liu Yueyao Fan Ting Cao Di Xiao
Motivated by recent experimental observations of opposite Chern numbers in $R$-type twisted MoTe$_2$ and WSe$_2$ homobilayers, we perform large-scale density-functional-theory (DFT) calculations with machine learning force fields to investigate moir\'e band topology from large to small twist angels in both materials. We find that the Chern numbers of the moir\'e frontier bands change sign as a function of twist angle, and this change is driven by the competition between the in-plane piezoelectricity and the out-of-plane ferroelectricity. Our large-scale calculations, enabled by machine learning methods, reveal crucial insights into interactions across different scales in twisted bilayer systems. The interplay between atomic-level relaxation effects and moir\'e-scale electrostatic potential variation opens new avenues for the design of intertwined topological and correlated states.

On topological order in higher composites
Egor Babaev
The recent experiments reported observation of a state with symmetry-breaking appearing at the level of four-electron order parameter (electronic quadruplets condensation) in a multicomponent system. This is in contrast to the conventional case where order appears at the level of electron pairing fields. Related states were theoretically demonstrated in mixtures of ultracold atoms. Here, we discuss the topological counterparts of this concept, i.e., topological order appearing only in higher-than-usual composites under somewhat related circumstances in multicomponent systems.

Antipersistent energy current correlations in strong long-ranged Fermi-Pasta-Ulam-Tsingou type models
Daxing Xiong Jianjin Wang
We study heat transfer in one-dimensional Fermi-Pasta-Ulam-Tsingou type systems with long-range (LR) interactions. The strength of the LR interaction between two lattice sites decays as a power $\sigma$ of the inverse of their distance. We focus on the strong LR regime ($0\leq \sigma \leq1$) and show that the thermal transport behaviors are remarkably nuanced. Specifically, we observe that the antipersistent (negative) energy current correlation in this regime is intricately dependent on $\sigma$, displaying a nonmonotonic variation. Notably, a significant qualitative change occurs at $\sigma_c=1/2$, where with respect to other $\sigma$ values, the correlation shows a minimum negative value. Furthermore, our findings demonstrate that within the long-time range considered, these antipersistent correlations eventually vanish for $\sigma$ approximately $\sigma \geq 0.7$. The underlying mechanisms behind these intriguing phenomena are related to the two diverse space-time scaling properties of equilibrium heat correlations and the various scattering processes of phonons and discrete breathers.

Mixed-state quantum anomaly and multipartite entanglement
Leonardo A. Lessa Meng Cheng Chong Wang
Quantum entanglement measures of many-body states have been increasingly useful to characterize phases of matter. Here we explore a surprising connection between mixed state entanglement and 't Hooft anomaly. More specifically, we consider lattice systems in $d$ space dimensions with anomalous symmetry $G$ where the anomaly is characterized by an invariant in the group cohomology $H^{d+2}(G,U(1))$. We show that any mixed state $\rho$ that is strongly symmetric under $G$, in the sense that $G\rho\propto\rho$, is necessarily $(d+2)$-nonseparable, i.e. is not the mixture of tensor products of $d+2$ states in the Hilbert space. Furthermore, such states cannot be prepared from any $(d+2)$-separable states using finite-depth local quantum channels, so the nonseparability is long-ranged in nature. We provide proof of these results in $d\leq1$, and plausibility arguments in $d>1$. The anomaly-nonseparability connection thus allows us to generate simple examples of mixed states with nontrivial long-ranged multipartite entanglement (even in $d=1$). We also briefly discuss mixed anomaly involving both strong and weak symmetries, including systems constrained by the Lieb-Schultz-Mattis type of anomaly.

Found 11 papers in prb
Date of feed: Fri, 09 Feb 2024 04:17:13 GMT

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

Magnetic properties, magnetic structure, and possible magnetoelectric effect in orthorhombic corundumlike ${\mathrm{Li}}_{2}{\mathrm{Ni}}_{2}{\mathrm{W}}_{2}{\mathrm{O}}_{9}$
Simon Redor, Maxim Avdeev, David Hrabovsky, Jean-Marie Tarascon, and Gwenaëlle Rousse
Author(s): Simon Redor, Maxim Avdeev, David Hrabovsky, Jean-Marie Tarascon, and Gwenaëlle Rousse

The magnetoelectric effect is an appealing property displayed by most compounds in the corundum-derived 429 series (${M}_{4}{A}_{2}{\mathrm{O}}_{9}, A=\mathrm{Nb}$ or Ta). The exception is ${\mathrm{Ni}}_{4}{\mathrm{Nb}}_{2}{\mathrm{O}}_{9}$, crystallizing in the orthorhombic Pbcn space group: becau…

[Phys. Rev. B 109, 054105] Published Thu Feb 08, 2024

Emergent strong zero mode through local Floquet engineering
Bhaskar Mukherjee, Ronald Melendrez, Marcin Szyniszewski, Hitesh J. Changlani, and Arijeet Pal
Author(s): Bhaskar Mukherjee, Ronald Melendrez, Marcin Szyniszewski, Hitesh J. Changlani, and Arijeet Pal

Periodically driven quantum systems host exotic phenomena that often do not have any analog in undriven systems. Floquet prethermalization and dynamical freezing of certain observables, via the emergence of conservation laws, are realized by controlling the drive frequency. Recent experimental devel…

[Phys. Rev. B 109, 064303] Published Thu Feb 08, 2024

Topological phases of strongly interacting time-reversal invariant topological superconducting chains under a magnetic field
Leandro M. Chinellato, Claudio J. Gazza, Alejandro M. Lobos, and Armando A. Aligia
Author(s): Leandro M. Chinellato, Claudio J. Gazza, Alejandro M. Lobos, and Armando A. Aligia

Using the density-matrix renormalization group, we determine the different topological phases and low-energy excitations of a time-reversal invariant topological superconducting (TRITOPS) wire with extended $s$-wave superconductivity, Rashba spin-orbit coupling (SOC) and on-site repulsion $U$, under…

[Phys. Rev. B 109, 064503] Published Thu Feb 08, 2024

Kitaev ring threaded by a magnetic flux: Topological gap, Anderson localization of quasiparticles, and divergence of supercurrent derivative
Martina Minutillo, Procolo Lucignano, Gabriele Campagnano, and Angelo Russomanno
Author(s): Martina Minutillo, Procolo Lucignano, Gabriele Campagnano, and Angelo Russomanno

We study a superconducting Kitaev ring pierced by a magnetic flux, with and without disorder, in a quantum ring configuration, and in a rf-SQUID one, where a weak link is present. In the rf-SQUID configuration, in the topological phase, the supercurrent shows jumps at specific values of the flux ${\…

[Phys. Rev. B 109, 064504] Published Thu Feb 08, 2024

Electrostatic environment and Majorana bound states in full-shell topological insulator nanowires
Li Chen, Xiao-Hong Pan, Zhan Cao, Dong E. Liu, and Xin Liu
Author(s): Li Chen, Xiao-Hong Pan, Zhan Cao, Dong E. Liu, and Xin Liu

The combination of a superconductor (SC) and a topological insulator (TI) nanowire was proposed as a potential candidate for realizing Majorana zero modes (MZMs). In this study, we adopt the Schrödinger-Poisson formalism to incorporate the electrostatic environment inside the nanowire and systematic…

[Phys. Rev. B 109, 075408] Published Thu Feb 08, 2024

Gapped Dirac materials and quantum valley currents in dual-gated hBN/bilayer-graphene heterostructures
Takuya Iwasaki, Yoshifumi Morita, Kenji Watanabe, and Takashi Taniguchi
Author(s): Takuya Iwasaki, Yoshifumi Morita, Kenji Watanabe, and Takashi Taniguchi

In gapped Dirac materials, the topological current associated with each valley can flow in opposite directions creating long-range charge-neutral valley currents. We report valley currents in hexagonal boron nitride (hBN)/bilayer-graphene heterostructures with an energy gap, which is tunable by a pe…

[Phys. Rev. B 109, 075409] Published Thu Feb 08, 2024

Quantum Hall effect in a Weyl-Hubbard model: Interplay between topology and correlation
Snehasish Nandy, Christopher Lane, and Jian-Xin Zhu
Author(s): Snehasish Nandy, Christopher Lane, and Jian-Xin Zhu

The interplay between topology and electronic correlations offer a rich avenue for discovering emergent quantum phenomena in condensed matter systems. In this work, starting from the Weyl-Hubbard model, we investigate the quantum Hall effect to explore the consequence of onsite Hubbard repulsion on …

[Phys. Rev. B 109, 085111] Published Thu Feb 08, 2024

Two-dimensional lattice with an imaginary magnetic field
Tomoki Ozawa and Tomoya Hayata
Author(s): Tomoki Ozawa and Tomoya Hayata

We introduce a two-dimensional non-Hermitian lattice model with an imaginary magnetic field and elucidate various unique features which are absent in Hermitian lattice models with real magnetic fields. To describe the imaginary magnetic field, we consider both the Landau gauge and the symmetric gaug…

[Phys. Rev. B 109, 085113] Published Thu Feb 08, 2024

Quantum thermodynamics: Inside-outside perspective
Jiayang Zhou, Anqi Li, and Michael Galperin
Author(s): Jiayang Zhou, Anqi Li, and Michael Galperin

We introduce an energy-resolved variant of quantum thermodynamics for open systems strongly coupled to their baths. The approach generalizes the Landauer-Buttiker inside-outside duality method [Phys. Rev. Lett. 120, 107701 (2018)] to interacting systems subjected to arbitrary external driving. It is…

[Phys. Rev. B 109, 085408] Published Thu Feb 08, 2024

Photoinduced dynamics of flat bands in the kagome metal CoSn
D. Puntel, W. Bronsch, M. Tuniz, M. Kang, P. M. Neves, S. Fang, E. Kaxiras, J. G. Checkelsky, R. Comin, F. Parmigiani, and F. Cilento
Author(s): D. Puntel, W. Bronsch, M. Tuniz, M. Kang, P. M. Neves, S. Fang, E. Kaxiras, J. G. Checkelsky, R. Comin, F. Parmigiani, and F. Cilento

CoSn is a prototypical kagome compound showing lattice-born flat bands with suppressed bandwidth over large parts of the Brillouin zone. Here, by means of time- and angle-resolved photoelectron spectroscopy, we provide direct evidence of the response to photoexcitation of the flat bands, which under…

[Phys. Rev. B 109, L081104] Published Thu Feb 08, 2024

Flat bands promoted by Hund's rule coupling in the candidate double-layer high-temperature superconductor ${\mathrm{La}}_{3}{\mathrm{Ni}}_{2}{\mathrm{O}}_{7}$ under high pressure
Yingying Cao and Yi-feng Yang
Author(s): Yingying Cao and Yi-feng Yang

This work describes systematic strongly correlated electronic structure calculations for the candidate double-layer high-temperature superconductor La3Ni2O7 under pressure. These reveal the localized-itinerant duality of Ni dz2 electrons, flat dz2 and dx2y2 quasiparticle bands, and strong interlayer antiferromagnetic correlations due to the interplay of orbital-selective Mott, Hund, and Kondo physics. These results imply a two-component theory with possibly preformed interlayer pairing for the high-temperature superconductivity in pressurized La3Ni2O7. The strange metallicity in the normal state is also explained from the quasiparticle lifetimes.

[Phys. Rev. B 109, L081105] Published Thu Feb 08, 2024

Found 4 papers in prl
Date of feed: Fri, 09 Feb 2024 04:17:14 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)

Detecting High-Energy Neutrinos from Galactic Supernovae with ATLAS
Alex Y. Wen, Carlos A. Argüelles, Ali Kheirandish, and Kohta Murase
Author(s): Alex Y. Wen, Carlos A. Argüelles, Ali Kheirandish, and Kohta Murase

We show that ATLAS, a collider detector, can measure the flux of high-energy supernova neutrinos, which can be produced from days to months after the explosion. Using Monte Carlo simulations for predicted fluxes, we find at most $\mathcal{O}(0.1–1)$ starting events and $\mathcal{O}(10–100)$ throughg…

[Phys. Rev. Lett. 132, 061001] Published Thu Feb 08, 2024

Observation of Higher-Order Nodal-Line Semimetal in Phononic Crystals
Qiyun Ma, Zhenhang Pu, Liping Ye, Jiuyang Lu, Xueqin Huang, Manzhu Ke, Hailong He, Weiyin Deng, and Zhengyou Liu
Author(s): Qiyun Ma, Zhenhang Pu, Liping Ye, Jiuyang Lu, Xueqin Huang, Manzhu Ke, Hailong He, Weiyin Deng, and Zhengyou Liu

The sound waves in a fabricated material exhibit topological features in one, two, and three dimensions—demonstrating an acoustic version of a higher-order nodal-line semimetal.

[Phys. Rev. Lett. 132, 066601] Published Thu Feb 08, 2024

Realization of Gapped and Ungapped Photonic Topological Anderson Insulators
Mina Ren, Ye Yu, Bintao Wu, Xin Qi, Yiwei Wang, Xiaogang Yao, Jie Ren, Zhiwei Guo, Haitao Jiang, Hong Chen, Xiong-Jun Liu, Zhigang Chen, and Yong Sun
Author(s): Mina Ren, Ye Yu, Bintao Wu, Xin Qi, Yiwei Wang, Xiaogang Yao, Jie Ren, Zhiwei Guo, Haitao Jiang, Hong Chen, Xiong-Jun Liu, Zhigang Chen, and Yong Sun

It is commonly believed that topologically nontrivial one-dimensional systems support edge states rather than bulk states at zero energy. In this work, we find an unanticipated case of topological Anderson insulator (TAI) phase where two bulk modes are degenerate at zero energy, in addition to degen…

[Phys. Rev. Lett. 132, 066602] Published Thu Feb 08, 2024

Duality and Sheared Analytic Response in Mechanism-Based Metamaterials
Michael Czajkowski and D. Zeb Rocklin
Author(s): Michael Czajkowski and D. Zeb Rocklin

Mechanical metamaterials designed around a zero-energy pathway of deformation known as a mechanism, challenge the conventional picture of elasticity and generate complex spatial response that remains largely uncharted. Here, we present a unified theoretical framework to showing that the presence of …

[Phys. Rev. Lett. 132, 068201] Published Thu Feb 08, 2024

Found 1 papers in pr_res
Date of feed: Fri, 09 Feb 2024 04:17:12 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)

Capturing near-field circular dichroism enhancements from far-field measurements
Jorge Olmos-Trigo, Jon Lasa-Alonso, Iker Gómez-Viloria, Gabriel Molina-Terriza, and Aitzol García-Etxarri
Author(s): Jorge Olmos-Trigo, Jon Lasa-Alonso, Iker Gómez-Viloria, Gabriel Molina-Terriza, and Aitzol García-Etxarri

Molecular circular dichroism (CD) spectroscopy faces significant limitations due to the inherent weakness of chiroptical light-matter interactions. In this view, resonant optical antennas constitute a promising solution to this problem, since they can be tuned to increase the CD enhancement factor, …

[Phys. Rev. Research 6, 013151] Published Thu Feb 08, 2024

Found 3 papers in nano-lett
Date of feed: Thu, 08 Feb 2024 14:16:33 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] Atomically Thin Current Pathways in Graphene through Kekulé-O Engineering
Santiago Galván y García, Yonatan Betancur-Ocampo, Francisco Sánchez-Ochoa, and Thomas Stegmann

TOC Graphic

Nano Letters
DOI: 10.1021/acs.nanolett.3c04703

[ASAP] Coexistence of Ferroelectricity and Ferromagnetism in Atomically Thin Two-Dimensional Cr2S3/WS2 Vertical Heterostructures
Luying Song, Ying Zhao, Ruofan Du, Hui Li, Xiaohui Li, Wang Feng, Junbo Yang, Xia Wen, Ling Huang, Yanan Peng, Hang Sun, Yulin Jiang, Jun He, and Jianping Shi

TOC Graphic

Nano Letters
DOI: 10.1021/acs.nanolett.3c05105

[ASAP] Graphene Hybrid Tough Hydrogels with Nanostructures for Tissue Regeneration
Yonghyun Gwon, Sangbae Park, Woochan Kim, Sunho Park, Harshita Sharma, Hoon Eui Jeong, Hyunjoon Kong, and Jangho Kim

TOC Graphic

Nano Letters
DOI: 10.1021/acs.nanolett.3c04188

Found 1 papers in acs-nano
Date of feed: Thu, 08 Feb 2024 14:12:21 GMT

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[ASAP] Advancing Molecular Sieving via Å-Scale Pore Tuning in Bottom-Up Graphene Synthesis
Cédric Van Goethem, Yueqing Shen, Heng-Yu Chi, Mounir Mensi, Kangning Zhao, Arian Nijmeijer, Paul-Emmanuel Just, and Kumar Varoon Agrawal

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ACS Nano
DOI: 10.1021/acsnano.3c11885

Found 1 papers in nat-comm

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

Interacting topological quantum chemistry in 2D with many-body real space invariants
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Found 1 papers in comm-phys

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Magnetic, transport and topological properties of Co-based shandite thin films
Yukitoshi Motome

Communications Physics, Published online: 05 February 2024; doi:10.1038/s42005-024-01534-8

The Weyl semimetal represents a distinctive topological state of matter, yet understanding its behaviour in thin films remains challenging, despite its significance for device applications. The authors reveal the layer number dependence of the band topology and transport properties in atomically thin films of a ferromagnetic Weyl semimetal, Co shandite.