Found 26 papers in cond-mat
Date of feed: Thu, 09 Nov 2023 01:30:00 GMT

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

Magnetic functionalization and Catalytic behavior of magnetic nanoparticles during laser photochemical graphitization of polyimide. (arXiv:2311.04264v1 [cond-mat.mtrl-sci])
Abhishek Sarkar, Ho-won Noh, Ikenna Nlebedim, Prana Shrotriya

We report laser-assisted photochemical graphitization of polyimides (PI) into functional magnetic nanocomposites using laser irradiation of PI in the presence of magnetite nanoparticles (MNP). PI Kapton sheets covered with MNP were photochemically treated under ambient conditions using a picosecond pulsed laser (1064nm) to obtain an electrically conductive material. Scanning electron microscopy of the treated material revealed layered magnetic nanoparticles/graphite nanocomposite structure (MNP/graphite). Four probe conductivity measurements indicated that nanocomposite has an electrical conductivity of 1550 S/m. Superconducting quantum interference device (SQUID) magnetometer-based magnetic characterization of the treated material revealed an anisotropic ferromagnetic response in the MNP/graphite nanocomposite compared to the isotropic response of MNP. Raman spectroscopy of MNP/graphite nanocomposite revealed a four-fold improvement in graphitization, suppression in disorder, and decreased nitrogenous impurities compared to the graphitic material obtained from laser treatment of just PI sheets. X-ray photoelectron spectroscopy, x-ray diffraction, and energy-dispersive x-ray spectroscopy were used to delineate the phase transformations of MNP during the formation of MNP/graphite nanocomposite. Post-mortem characterization indicates a possible photocatalytic effect of MNP during MNP/graphite nanocomposite formation. Under laser irradiation, MNP transformed from the initial Fe3O4 phase to {\gamma}-Fe2O3 and Fe5C2 phases and acted as nucleation spots to catalyze the graphitization process of PI.

The Pressure-Stabilized Polymorph of Indium Triiodide. (arXiv:2311.04332v1 [cond-mat.mtrl-sci])
Danrui Ni, Haozhe Wang, Xianghan Xu, Weiwei Xie, Robert J. Cava

A layered rhombohedral polymorph of indium (III) triiodide is synthesized at high pressure and temperature. The unit cell symmetry and approximate dimensions are determined by single crystal X-ray diffraction. Its R-3 crystal structure, with a = 7.217 {\AA}, and c = 20.476 {\AA}, is refined by the Rietveld method on powder X-ray diffraction data. The crystal structure is based on InI6 octahedra sharing edges to form honeycomb lattice layers, though with considerable stacking variations. Different from ambient pressure InI3, which has a monoclinic molecular structure and a light-yellow color, high pressure InI3 is layered and has an orange color. The band gaps of both the monoclinic and rhombohedral variants of InI3 are estimated from diffuse reflectance measurements.

Patterning edge-like defects and tuning defective areas on the basal plane of ultra-large MoS$_{2}$ monolayers toward hydrogen evolution reaction. (arXiv:2311.04413v1 [cond-mat.mtrl-sci])
Bianca Rocha Florindo, Leonardo H. Hasimoto, Nicolli de Freitas, Graziâni Candiotto, Erika Nascimento Lima, Cláudia de Lourenço, Ana B. S. de Araujo, Carlos Ospina, Jefferson Bettini, Edson R. Leite, Renato S. Lima, Adalberto Fazzio, Rodrigo B. Capaz, Murilo Santhiago

The catalytic sites of MoS$_{2}$ monolayers towards hydrogen evolution are well known to be vacancies and edge-like defects. However, it is still very challenging to control the position, size, and defective areas on the basal plane of Mo$S_{2}$ monolayers by most of defect-engineering routes. In this work, the fabrication of etched arrays on ultra-large supported and free-standing MoS$_{2}$ monolayers using focused ion beam (FIB) is reported for the first time. By tuning the Ga+ ion dose, it is possible to confine defects near the etched edges or spread them over ultra-large areas on the basal plane. The electrocatalytic activity of the arrays toward hydrogen evolution reaction (HER) was measured by fabricating microelectrodes using a new method that preserves the catalytic sites. We demonstrate that the overpotential can be decreased up to 290 mV by assessing electrochemical activity only at the basal plane. High-resolution transmission electron microscopy images obtained on FIB patterned freestanding MoS$_{2}$ monolayers reveal the presence of amorphous regions and X-ray photoelectron spectroscopy indicates sulfur excess in these regions. Density-functional theory calculations provide identification of catalytic defect sites. Our results demonstrate a new rational control of amorphous-crystalline surface boundaries and future insight for defect optimization in MoS$_{2}$ monolayers.

AI-accelerated Discovery of Altermagnetic Materials. (arXiv:2311.04418v1 [cond-mat.mtrl-sci])
Ze-Feng Gao, Shuai Qu, Bocheng Zeng, Ji-Rong Wen, Hao Sun, Pengjie Guo, Zhong-Yi Lu

Altermagnetism, a new magnetic phase, has been theoretically proposed and experimentally verified to be distinct from ferromagnetism and antiferromagnetism. Although altermagnets have been found to possess many exotic physical properties, the very limited availability of known altermagnetic materials~(e.g., 14 confirmed materials) hinders the study of such properties. Hence, discovering more types of altermagnetic materials is crucial for a comprehensive understanding of altermagnetism and thus facilitating new applications in the next generation information technologies, e.g., storage devices and high-sensitivity sensors. Here, we report 25 new altermagnetic materials that cover metals, semiconductors, and insulators, discovered by an AI search engine unifying symmetry analysis, graph neural network pre-training, optimal transport theory, and first-principles electronic structure calculation. The wide range of electronic structural characteristics reveals that various innovative physical properties manifest in these newly discovered altermagnetic materials, e.g., anomalous Hall effect, anomalous Kerr effect, and topological property. Noteworthy, we discovered 8 $i$-wave altermagnetic materials for the first time. Overall, the AI search engine performs much better than human experts and suggests a set of new altermagnetic materials with unique properties, outlining its potential for accelerated discovery of altermagnetic materials.

Kekul\'e valence bond order in the Hubbard model on the honeycomb lattice with possible lattice distortions for graphene. (arXiv:2311.04469v1 [cond-mat.str-el])
Yuichi Otsuka, Seiji Yunoki

We investigate if and how the valence-bond-solid (VBS) state emerges in the Hubbard model on the honeycomb lattice when the Peierls-type electron-lattice coupling is introduced. We consider all possible lattice-distortion patterns allowed for this lattice model for graphene which preserve the reflection symmetry and determine the most stable configuration in the adiabatic limit by using an unbiased quantum Monte Carlo method. The VBS phase with Kekul\'e dimerization is found to appear as an intermediate phase between a semimetal and an antiferromagnetic Mott insulator for a moderately rigid lattice. This implies that the undistorted semimetallic graphene can be driven into the VBS phase by applying strain, accompanied by the single-particle excitation gap opening.

Projective symmetry determined topology in flux Su-Schrieffer-Heeger model. (arXiv:2311.04516v1 [cond-mat.mes-hall])
Gang Jiang, Z. Y. Chen, S. J. Yue, W. B. Rui, Xiao-Ming Zhu, Shengyuan A. Yang, Y. X. Zhao

In the field of symmetry-protected topological phases, a common wisdom is that the symmetries fix the topological classifications, but they alone cannot determine whether a system is topologically trivial or not. Here, we show that this is no longer true in cases where symmetries are projectively represented. Particularly, the Zak phase, a topological invariant of a one-dimensional system, can be entirely determined by the projective symmetry algebra (PSA). To demonstrate this remarkable effect, we propose a minimal model, termed as flux Su-Schrieffer-Heeger (SSH) model, where the bond dimerization in the original SSH model is replaced by a flux dimerization. We present experimental realization of our flux SSH model in an electric-circuit array, and our predictions are directly confirmed by experimental measurement. Our work refreshes the understanding of the relation between symmetry and topology, opens up new avenues for exploring PSA determined topological phases, and suggests flux dimerization as a novel approach for designing topological crystals.

Active search for a reactive target in thermal environments. (arXiv:2311.04539v1 [cond-mat.stat-mech])
Byeong Guk Go, Euijin Jeon, Yong Woon Kim

We study a stochastic process where an active particle, modeled by a one-dimensional run-and-tumble particle, searches for a target with a finite absorption strength in thermal environments. Solving the Fokker-Planck equation for a uniform initial distribution, we analytically calculate the mean searching time (MST), the time for the active particle to be finally absorbed, and show that there exists an optimal self-propulsion velocity of the active particle at which MST is minimized. As the diffusion constant increases, the optimal velocity changes from a finite value to zero, which implies that a purely diffusive Brownian motion outperforms an active motion in terms of searching time. Depending on the absorption strength of the target, the transition of the optimal velocity becomes either continuous or discontinuous, which can be understood based on the Landau approach. In addition, we obtain the phase diagram indicating the passive-efficient and the active-efficient regions. Finally, the initial condition dependence of MST is presented in limiting cases.

Determining the molecular Huang-Rhys factor via STM induced luminescence. (arXiv:2311.04543v1 [cond-mat.mes-hall])
Fei Wen, Guohui Dong

The scanning tunneling microscopy induced luminescence (STML) can be used to probe the optical and electronic properties of molecules. Concerning the vibronic coupling, we model the molecule as a two-level system with the vibrational degrees of freedom. Based on the Bardeen's theory, we express the inelastic tunneling current in terms of Huang-Rhys factor within the inelastic electron scattering (IES) mechanism. We find that the differential conductance, varying with the bias voltage, exhibits distinct step structure with various vibronic coupling strength. The second derivative of the inelastic tunneling current with respect to the bias voltage shows the characteristics of vibrational-level structure with Franck-Condon factor. Consequently, we propose a method to determine the Huang-Rhys factor of molecules, holding promising potential within the realm of solid-state physics.

Photon absorption in twisted bilayer graphene. (arXiv:2311.04565v1 [cond-mat.mes-hall])
Disha Arora, Deepanshu Aggarwal, Sankalpa Ghosh, Rohit Narula

We investigate one- and two-photon absorption in twisted bilayer graphene (TBLG) by examining the effects of tuning the twist angle $ \theta $ and the excitation energy $ E_l $ on their corresponding absorption coefficients $ \alpha_{i=1,2}$. We find that $ \alpha_1 $ shows distinct peaks as a function of $ E_l $ which correspond to the van Hove singularities (vHS) of TBLG. In contrast to single- (SLG) and AB bilayer graphene (BLG), $ \alpha_1 $ is substantially enhanced by $\sim 2$ and $\sim 1$ orders of magnitude, respectively, in the visible range. On the other hand, $\alpha_2 $ exhibits a remarkable increase of $\sim 11$ and $\sim 9$ orders of magnitude. Interestingly, as $\theta$ increases, the resonant features exhibited by $\alpha_{i=1,2}$ \textit{vs.} $ E_l $ shift progressively from the infrared to the visible. On doping TBLG, both $\alpha_1 $ and $ \alpha_2 $ remain essentially unchanged \textit{vs.} $ E_l $ but with a minor red-shift in their resonant peaks. Additionally, we explore various polarization configurations for TPA and determine the conditions under which $\alpha_2$ becomes extremal.

Restoring symmetries in quantum computing using Classical Shadows. (arXiv:2311.04571v1 [quant-ph])
Edgar Andres Ruiz Guzman, Denis Lacroix

We introduce a method to enforce some symmetries starting from a trial wave-function prepared on quantum computers that might not respect these symmetries. The technique eliminates the necessity for performing the projection on the quantum computer itself. Instead, this task is conducted as a post-processing step on the system's "Classical Shadow". Illustrations of the approach are given for the parity, particle number, and spin projectors that are of particular interest in interacting many-body systems. We compare the method with another classical post-processing technique based on direct measurements of the quantum register. We show that the present scheme can be competitive to predict observables on symmetry-restored states once optimization through derandomization is employed. The technique is illustrated through its application to compute the projected energy for the pairing model Hamiltonian.

Non-Hermitian Aubry-Andr\'e-Harper model with short- and long-range p-wave pairing. (arXiv:2311.04605v1 [cond-mat.dis-nn])
Shaina Gandhi, Jayendra N. Bandyopadhyay

We investigate a non-Hermitian Aubry-Andre-Harper model, considering both the short- and long-range p-wave pairing. Here, the non-Hermiticity is considered at the onsite potential. A comprehensive analysis of several critical aspects of this system, including the eigenspectra, localization properties, PT} symmetry, real to complex transition, and topological properties, is conducted. Specifically, we observe the emergence of Majorana zero modes in the case of short-range pairing, whereas the massive Dirac modes emerge in the case of long-range pairing. Notably, a triple-phase transition is identified, involving simultaneous transitions from extended or metallic state to critical multifractal state, unbroken to broken PT symmetry, and unconventional real to complex energies. In addition, a double-phase transition is observed, where the topological and superconducting transitions occur concurrently. These intriguing double- and triple-phase transitions are observed in both short- and long-range pairing cases.

Mechanical strain induced topological phase changes of few layer ZrTe$_5$. (arXiv:2311.04721v1 [cond-mat.mtrl-sci])
Zoltán Tajkov, Konrád Kandrai, Dániel Nagy, Levente Tapasztó, János Koltai, Péter Nemes-Incze

Understanding the topological aspects of the band structure of solids has fundamentally changed our appreciation of their properties. The layered, van der Waals transition-metal pentatelluride ZrTe$_5$ has proven on numerous occasions to be an excellent candidate for the study of controllable topological phase transitions. Here, we investigate the topological phase diagrams of monolayer and bilayer forms of ZrTe$_5$, under mechanical deformations using \textit{ab initio} techniques. We find that mechanical deformation can close the monolayer's topological gap, while the bilayer exhibits richer phase diagram, including both topological insulating, trivial metallic and insulating phases. The bilayer is predicted to be on the topological phase boundary. We also address the preparation of monolayers, using \emph{ab initio} simulations and experimental scanning tunneling microscopy measurements. We confirm that while monolayer ZrTe$_5$ is difficult to exfoliate without compromising its crystalline structure, bilayers offer a more stable alternative, revealing the complexities and limitations of using gold substrates for monolayer exfoliation.

Tailoring bistability in optical tweezers with vortex beams and spherical aberration. (arXiv:2311.04737v1 [physics.optics])
Arthur Luna da Fonseca, Kainã Diniz, Paula Borges Monteiro, Luís Barbosa Pires, Guilherme Tenório Moura, Mateus Borges, Rafael de Sousa Dutra, Diney Soares Ether Jr, Nathan Bessa Viana, Paulo Américo Maia Neto

We demonstrate a bistable optical trap by tightly focusing a vortex laser beam. The optical potential has the form of a Mexican hat with an additional minimum at the center. The bistable trapping corresponds to a non-equilibrium steady state (NESS), where the microsphere continually hops, due to thermal activation, between an axial equilibrium state and an orbital state driven by the optical torque. We develop a theoretical model for the optical force field, based entirely on experimentally accessible parameters, combining a Debye-type non-paraxial description of the focused vortex beam with Mie scattering by the microsphere. The theoretical prediction that the microsphere and the annular laser focal spot should have comparable sizes is confirmed experimentally by taking different values for the topological charge of the vortex beam. Spherical aberration introduced by refraction at the interface between the glass slide and the sample is taken into account and allows to fine tune between axial, bistable and orbital states as the sample is shifted with respect to the objective focal plane. We find an overall agreement between theory and experiment for a rather broad range of topological charges. Our results open the way for applications in stochastic thermodynamics as it establishes a new control parameter, the height of the objective focal plane with respect to the glass slide, that allows to shape the optical force field in real time and in a controllable way.

Phase diagram near the quantum critical point in Schwinger model at $\theta = \pi$: analogy with quantum Ising chain. (arXiv:2311.04738v1 [hep-lat])
Hiroki Ohata

The Schwinger model, one-dimensional quantum electrodynamics, has CP symmetry at $\theta = \pi$ due to the topological nature of the $\theta$ term. At zero temperature, it is known that as increasing the fermion mass, the system undergoes a second-order phase transition to the CP broken phase, which belongs to the same universality class as the quantum Ising chain. In this paper, we explore the phase diagram near the quantum critical point (QCP) in the temperature and fermion mass plane using first-principle Monte Carlo simulations, while avoiding the sign problem by using the lattice formulation of the bosonized Schwinger model. Specifically, we perform a detailed investigation of the correlation function of the electric field near the QCP and find that its asymptotic behavior can be described by the universal scaling function of the quantum Ising chain. This finding indicates the existence of three regions near the QCP, each characterized by a specific asymptotic form of the correlation length, and demonstrates that the CP symmetry is restored at any nonzero temperature, entirely analogous to the quantum Ising chain. The range of the scaling behavior is also examined and found to be particularly wide.

Magnetostriction of metals with small Fermi-surface pockets: the case of the topologically trivial semimetal LuAs. (arXiv:2311.04768v1 [cond-mat.mtrl-sci])
Yu. V. Sharlai, L. Bochenek, J. Juraszek, T. Cichorek, G. P. Mikitik

We develop a theory of the magnetostriction for metals with small charge-carrier pockets of their Fermi surfaces. As an example, we consider LuAs that has a cubic crystal structure. The theory quite well describes the known experimental data on the magnetostriction of this metal. The obtained results also clearly demonstrate that the dilatometry can be used for detecting tiny Fermi-surface pockets that are not discerned by traditional methods based on investigations of the Shubnikov--de Haas and de Haas--van Alphen effects.

Spatially twisted liquid-crystal devices. (arXiv:2311.04773v1 [physics.optics])
Alicia Sit, Francesco Di Colandrea, Alessio D'Errico, Ebrahim Karimi

Nematic liquid-crystal devices are a powerful tool to structure light in different degrees of freedom, both in classical and quantum regimes. Most of these devices exploit either the possibility of introducing a position-dependent phase retardation with a homogeneous alignment of the optic axis -- e.g., liquid-crystal-based spatial light modulators -- or conversely, with a uniform but tunable retardation and patterned optic axis, e.g., $q$-plates. The pattern is the same in the latter case on the two alignment layers. Here, a more general case is considered, wherein the front and back alignment layers are patterned differently. This creates a non-symmetric device which can exhibit different behaviours depending on the direction of beam propagation and effective phase retardation. In particular, we fabricate multi-$q$-plates by setting different topological charges on the two alignment layers. The devices have been characterized by spatially resolved Stokes polarimetry, with and without applied electric voltage, demonstrating new functionalities.

Real-space multifold degeneracy in graphene irradiated by twisted light. (arXiv:2311.04792v1 [cond-mat.mes-hall])
Suman Aich, Babak Seradjeh (IUB)

We report the theoretical discovery of real-space multifold degenerate Floquet-Bloch states in monolayer graphene coherently driven by twisted circulalry-polarized light. Using Floquet theory, we characterize the real-space structure of quasienergies and Floquet modes in terms of the orbital angular momentum and radial vortex profile of light. We obtain the effective real-space Floquet Hamiltonian and show it supports crossings of Floquet modes, especially at high-symmetry $K$ and $\Gamma$ points of graphene, at specific radial positions from the vortex center. At specific frequencies, the vortex bound states form a multifold degenerate structure in real-space. This structure is purely dynamically generated and controlled by the frequency and intensity of twisted light. We discuss the experimental feasibility of observing and employing the real-space multifold degeneracy for coherent optoelectronic quantum state engineering.

Linear dichroic x-ray absorption response of Ti-Ti dimers along the $c$ axis in Ti$_2$O$_3$ upon Mg substitution. (arXiv:2311.04814v1 [cond-mat.str-el])
M. Okawa, D. Takegami, D. S. Christovam, M. Ferreira-Carvalho, C.-Y. Kuo, C. T. Chen, T. Miyoshino, K. Takasu, T. Okuda, C. F. Chang, L. H. Tjeng, T. Mizokawa

Corundum oxide Ti$_2$O$_3$ shows the metal-insulator transition around 400-600 K accompanying the nearest Ti$^{3+}$-Ti$^{3+}$ bond ($a_{1g}a_{1g}$ singlet state) formation along the $c$ axis. In order to clarify the hole-doping effect for the $a_{1g}a_{1g}$ singlet bond in Ti$_2$O$_3$, we investigated Ti $3d$ orbital anisotropy between corundum-type Ti$_2$O$_3$ and ilmenite-type MgTiO$_3$ using linear dichroism of soft x-ray absorption spectroscopy of the Ti $L_{2,3}$ edge. From the linear dichroic spectral weight in Mg$_y$Ti$_{2-y}$O$_3$, we confirmed that the $a_{1g}a_{1g}$ state is dominant not only in $y=0.01$ (almost Ti$_2$O$_3$), but also in $y = 0.29$, indicating that the Ti-Ti bond survives against a certain level of hole doping. In $y=0.63$ corresponding to 46% hole doping per Ti, the $3d$ orbital symmetry changes from $a_{1g}$ to $e_g^{\pi}$.

Domain coarsening in polycrystalline graphene. (arXiv:2311.04842v1 [cond-mat.dis-nn])
Zihua Liu, Debabrata Panja, Gerard T. Barkema

Graphene is a two-dimensional carbon material which exhibits exceptional properties, making it highly suitable for a wide range of applications. Practical graphene fabrication often yields a polycrystalline structure with many inherent defects, which significantly influence its performance. In this study, we utilize a Monte Carlo approach based on the optimized Wooten, Winer and Weaire (WWW) algorithm to simulate the crystalline domain coarsening process of polycrystalline graphene. Our sample configurations show excellent agreement with experimental data. We conduct statistical analyses of the bond and angle distribution, temporal evolution of the defect distribution, and spatial correlation of the lattice orientation that follows a stretched exponential distribution. Furthermore, we thoroughly investigate the diffusion behavior of defects and find that the changes in domain size follow a power-law distribution. We briefly discuss the possible connections of these results to (and differences from) domain growth processes in other statistical models, such as the Ising dynamics. We also examine the impact of buckling of polycrystalline graphene on the crystallization rate under substrate effects. Our findings may offer valuable guidance and insights for both theoretical investigations and experimental advancements.

Cavity Soliton-Induced Topological Edge States. (arXiv:2311.04873v1 [physics.optics])
Christian R. Leefmans, Nicolas Englebert, James Williams, Robert M. Gray, Nathan Goldman, Simon-Pierre Gorza, François Leo, Alireza Marandi

Over the past decade, cavity solitons have attracted substantial attention for their rich dynamics and their myriad potential applications. Recently, there has been growing interest in understanding cavity solitons in systems of coupled resonators, where both new physics and applications can emerge. While numerous works have theoretically studied the interplay between cavity solitons and lattice topology, experimental demonstrations of cavity solitons in topological lattices remain elusive. Here, we experimentally realize cavity solitons in a Su-Schrieffer-Heeger (SSH) lattice and illustrate that the synergy between topology and soliton formation dynamics can induce soliton formation at the boundaries of a topological SSH lattice. Our work illustrates the rich physics of cavity solitons in topological lattices and demonstrates a flexible approach to study solitons in large-scale coupled resonator arrays.

Caution on Gross-Neveu criticality with a single Dirac cone: Violation of locality and its consequence of unexpected finite-temperature transition. (arXiv:2210.04272v2 [cond-mat.str-el] UPDATED)
Yuan Da Liao, Xiao Yan Xu, Zi Yang Meng, Yang Qi

Lately there are many SLAC fermion investigations on the (2+1)D Gross-Neveu criticality of a single Dirac cone [1,2]. While the SLAC fermion construction indeed gives rise to the linear energy-momentum relation for all lattice momenta at the non-interacting limit, the long-range hopping and its consequent violation of locality on the Gross-Neveu quantum critical point (GN-QCP) -- which a priori requires short-range interaction -- has not been verified. Here we show, by means of large-scale quantum Monte Carlo simulations, that the interaction-driven antiferromagnetic insulator in this case is fundamentally different from that on a purely local $\pi$-flux Hubbard model on the square lattice. In particular, we find the antiferromagnetic long-range order in the SLAC fermion model has a finite temperature continuous phase transition, which violates the Mermin-Wagner theorem, and smoothly connects to the previously determined GN-QCP. The magnetic excitations inside the antiferromagnetic insulator are gapped without Goldstone mode, even though the state spontaneously breaks continuous $SU(2)$ symmetry. These unusual results proclaim caution on the interpretation of the quantum phase transition in SLAC fermion model as that of GN-QCP with short-range interaction.

Realizing Majorana Kramers pairs in two-channel InAs-Al nanowires with highly misaligned electric fields. (arXiv:2304.07286v2 [cond-mat.mes-hall] UPDATED)
Benjamin D Woods, 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 eliminate magnetic fields, geometric constraints make their implementation challenging, since the channels should be immersed in nearly antiparallel electric fields. Here, we propose an experimentally favorable scheme for realizing field-free topological superconductivity, in two-channel InAs-Al nanowires, that overcomes such growth constraints. Crucially, we show that antiparallel fields are not required, if the channels are energetically detuned. We compute topological phase diagrams for realistically modeled nanowires, finding a broad range of parameters that could potentially harbor Majorana zero modes. This work, therefore, solves a major technical challenge and opens the door to near-term experiments.

Moir\'e fractals in twisted graphene layers. (arXiv:2306.04580v2 [cond-mat.mes-hall] UPDATED)
Deepanshu Aggarwal, Rohit Narula, Sankalpa Ghosh (IIT Delhi)

Twisted bilayer graphene (TBLG) subject to a sequence of commensurate external periodic potentials reveals the formation of moir\'{e} fractals (MF) that share striking similarities with the central place theory (CPT) of economic geography, thus uncovering a remarkable connection between twistronics and the geometry of economic zones. The MFs arise from the self-similarity of the emergent hierarchy of Brillouin zones (BZ), forming a nested subband structure within the bandwidth of the original moir\'{e} bands. The fractal generators for TBLG under these external potentials are derived and we explore their impact on the hierarchy of the BZ edges and the wavefunctions at the Dirac point. By examining realistic super-moir\'{e} structures (SMS) and demonstrating their equivalence to an MF with periodic perturbations under specific conditions, we establish MFs as a general description for such systems. Furthermore, we uncover parallels between the modification of the BZ hierarchy and magnetic BZ formation in the Hofstadter butterfly problem, allowing us to construct an incommensurability measure for MFs as a function of the twist angle. The resulting band structure hierarchy bolsters correlation effects, pushing more bands within the same energy window for both commensurate and incommensurate TBLG.

Linear response theories for interatomic exchange interactions. (arXiv:2308.04799v3 [cond-mat.mtrl-sci] UPDATED)
I. V. Solovyev

In 1987, Liechtenstein et al. came up with the idea to formulate the problem of interatomic exchange interactions, which would describe the energy change caused by the infinitesimal rotations of spins, in terms of the magnetic susceptibility. The formulation appears to be very generic and, for isotropic systems, expresses the energy change in the form of the Heisenberg model, irrespectively on which microscopic mechanism stands behind the interaction parameters. Moreover, this approach establishes the relationship between the exchange interactions and the electronic structure obtained, for instance, in the first-principles calculations based on the density functional theory. The purpose of this review is to elaborate basic ideas of the linear response theories for the exchange interactions as well as more recent developments. The special attention is paid to the approximations underlying the original method of Liechtenstein et al. in comparison with its more recent and more rigorous extensions, the roles of the on-site Coulomb interactions and the ligand states, and calculations of antisymmetric Dzyaloshinskii-Moriya interactions, which can be performed alongside with the isotropic exchange, within one computational scheme. The abilities of the linear response theories as well as many theoretical nuances, which may arise in the analysis of interatomic exchange interactions, are illustrated on magnetic van der Walls materials Cr$X_3$ ($X$$=$ Cl, I), half-metallic ferromagnet CrO$_2$, ferromagnetic Weyl semimetal Co$_3$Sn$_2$S$_2$, and orthorhombic manganites $A$MnO$_3$ ($A$$=$ La, Ho), known for the peculiar interplay of the lattice distortion, spin, and orbital ordering.

A first-principles study of bilayer 1T'-WTe2/CrI3: A candidate topological spin filter. (arXiv:2308.06415v2 [cond-mat.mes-hall] UPDATED)
Daniel Staros, Brenda Rubenstein, Panchapakesan Ganesh

The ability to manipulate electronic spin channels in 2D materials is crucial for realizing next-generation spintronics. Spin filters are spintronic components that polarize spins using external fields or material properties like magnetism. Recently, topological protection from backscattering has emerged as an enticing feature through which to enhance the robustness of 2D spin filters. In this work, we propose and then characterize one of the first 2D topological spin filters: bilayer CrI3/1T'-WTe2 (BLCW). To do so, we use a combination of DFT, maximally localized Wannier functions, and quantum transport simulations to demonstrate that the BLCW satisfies the principal criteria for being a topological spin filter; namely that it is gapless, exhibits spin-polarized charge transfer (SPCT) from WTe2 to CrI3 that renders the BLCW metallic, and has a topological boundary which retains the edge conductance of monolayer (ML) 1T'-WTe2. We observe that the atomic magnetic moments on Cr from DFT are approximately 3.2 mB/Cr in the BL compared to 2.9 mB/Cr with small negative ferromagnetic (FM) moments induced on the W atoms in freestanding ML CrI3. Subtracting the charge/spin densities of the constituent ML's from those of the BLCW further reveals SOC-enhanced SPCT from WTe2 to CrI3. We find that the BLCW is topologically trivial by showing that its Chern number is zero. Lastly, we show that interfacial scattering at the boundary between the terraced materials does not remove WTe2's edge conductance. This evidence indicates that BLCW is gapless, magnetic, and topologically trivial, meaning that a terraced WTe2/CrI3 BL heterostructure in which only a portion of a WTe2 ML is topped with CrI3 is a promising candidate for a 2D topological spin filter. Our results further suggest that 1D chiral edge states may be realized by stacking FM ML's, like CrI3, atop 2D nonmagnetic Weyl semimetals like 1T'-WTe2.

Landau-Zener transition rates of superconducting qubits and absorption spectrum in quantum dots. (arXiv:2310.13058v2 [quant-ph] UPDATED)
Jorge G. Russo, Miguel Tierz

New exact formulas are derived for systems involving Landau-Zener transition rates and for absorption spectra in quantum dots. A number of novel physical implications are explored in detail.

Found 7 papers in prb
Date of feed: Thu, 09 Nov 2023 04:16:59 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)

Crystal and magnetic structure of cesium superoxide
R. A. Ewings, M. Reehuis, F. Orlandi, P. Manuel, D. D. Khalyavin, A. S. Gibbs, A. D. Fortes, A. Hoser, A. J. Princep, and M. Jansen
Author(s): R. A. Ewings, M. Reehuis, F. Orlandi, P. Manuel, D. D. Khalyavin, A. S. Gibbs, A. D. Fortes, A. Hoser, A. J. Princep, and M. Jansen

Cesium superoxide is magnetic, due to the half-occupied π orbitals on its O2 molecules. Neutron diffraction experiments done here find that the crystal structure undergoes a sequence of transitions from tetragonal to incommensurate to orthorhombic, with the latter two exhibiting staggered displacements of the cesium ions. The symmetry of this structure permits antisymmetric exchange, which is consistent with a canted antiferromagnetic structure also observed, and a nice example of a structure-property relationship.

[Phys. Rev. B 108, 174412] Published Wed Nov 08, 2023

Assembling Kitaev honeycomb spin liquids from arrays of one-dimensional symmetry-protected topological phases
Yue Liu, Nathanan Tantivasadakarn, Kevin Slagle, David F. Mross, and Jason Alicea
Author(s): Yue Liu, Nathanan Tantivasadakarn, Kevin Slagle, David F. Mross, and Jason Alicea

The Kitaev honeycomb model, which is exactly solvable by virtue of an extensive number of conserved quantities, supports a gapless quantum spin liquid phase as well as gapped descendants relevant for fault-tolerant quantum computation. We show that the anomalous edge modes of one-dimensional (1D) cl…

[Phys. Rev. B 108, 184406] Published Wed Nov 08, 2023

Bidirectional magnon-driven bimeron motion in ferromagnets
Xue Liang, Jin Lan, Guoping Zhao, Mateusz Zelent, Maciej Krawczyk, and Yan Zhou
Author(s): Xue Liang, Jin Lan, Guoping Zhao, Mateusz Zelent, Maciej Krawczyk, and Yan Zhou

As the in-plane magnetized counterparts of skyrmions in two dimensions, magnetic bimerons are swirling topological spin textures consisting of two merons. Here we theoretically and numerically investigate the dynamics of a bimeron induced by the monochromatic spin wave in a ferromagnetic thin film. …

[Phys. Rev. B 108, 184407] Published Wed Nov 08, 2023

Proximity spin-orbit coupling in a small-diameter armchair carbon nanotube on monolayer bismuthene
Marcin Kurpas
Author(s): Marcin Kurpas

We study the spin-orbit proximity effects in a hybrid heterostructure built from a one-dimensional (1D) armchair carbon nanotube and two-dimensional (2D) buckled monolayer bismuthene. We show, by performing first-principles calculations, that Dirac electrons in the nanotube exhibit large spin-orbit …

[Phys. Rev. B 108, 195408] Published Wed Nov 08, 2023

Structure and dynamics of a pinned vortex liquid in a superconducting $a\text{−}{\mathrm{Re}}_{6}\mathrm{Zr}$ thin film
Rishabh Duhan, Subhamita Sengupta, Ruchi Tomar, Somak Basistha, Vivas Bagwe, Chandan Dasgupta, and Pratap Raychaudhuri
Author(s): Rishabh Duhan, Subhamita Sengupta, Ruchi Tomar, Somak Basistha, Vivas Bagwe, Chandan Dasgupta, and Pratap Raychaudhuri

Real space imaging using a scanning tunnelling microscope reveals the formation of an inhomogeneous vortex liquid state in few nanometer thick superconducting films that does not freeze into a crystal or a glass down to 0.41 K. Vortices in this two-dimensional liquid form a network of percolating paths, due to the combined effect of pinning and intervortex interaction. While some vortices remain static, others move on this network, with their relative fractions changing with magnetic field, temperature, and applied current.

[Phys. Rev. B 108, L180503] Published Wed Nov 08, 2023

Spectroscopic signature of spin triplet odd-valley superconductivity in two-dimensional materials
T. H. Kokkeler, Chunli Huang, F. S. Bergeret, and I. V. Tokatly
Author(s): T. H. Kokkeler, Chunli Huang, F. S. Bergeret, and I. V. Tokatly

Motivated by recent discoveries of superconductivity in lightly doped multilayer graphene systems, we present a low-energy model to study superconductivity in two-dimensional materials whose Fermi surface consists of two valleys at $±\mathbit{K}$ points. We assume a triplet odd-valley superconductin…

[Phys. Rev. B 108, L180504] Published Wed Nov 08, 2023

Laughlin's quasielectron as a nonlocal composite fermion
Alberto Nardin and Leonardo Mazza
Author(s): Alberto Nardin and Leonardo Mazza

We discuss the link between the quasielectron wave functions proposed by Laughlin and by Jain and show both analytically and numerically that Laughlin's quasielectron is a nonlocal composite-fermion state. Composite-fermion states are typically discussed in terms of the composite-fermion Landau leve…

[Phys. Rev. B 108, L201106] Published Wed Nov 08, 2023

Found 1 papers in prl
Date of feed: Thu, 09 Nov 2023 04:17:02 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)

A No-Go Result for Implementing Chiral Symmetries by Locality-Preserving Unitaries in a Three-Dimensional Hamiltonian Lattice Model of Fermions
Lukasz Fidkowski and Cenke Xu
Author(s): Lukasz Fidkowski and Cenke Xu

We argue that the chiral $\mathrm{U}(1{)}_{A}$ symmetry of a Weyl fermion cannot be implemented by a shallow depth quantum circuit operation in a fermionic lattice Hamiltonian model with finite dimensional onsite Hilbert spaces. We also extend this result to discrete ${\mathbb{Z}}_{2N}$ subgroups of…

[Phys. Rev. Lett. 131, 196601] Published Wed Nov 08, 2023

Found 2 papers in pr_res
Date of feed: Thu, 09 Nov 2023 04:17:02 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)

Comment on “Weak values and the past of a quantum particle”
Lev Vaidman
Author(s): Lev Vaidman

In a recent paper, Hance et al. [Phys. Rev. Res. 5, 023048 (2023)] criticized recent proposals connecting weak values and the past of a quantum particle. I argue that their conclusion follows from a conceptual error in understanding the approach to the past of the particle they discuss.

[Phys. Rev. Research 5, 048001] Published Wed Nov 08, 2023

Second-order perturbation theory in continuum quantum Monte Carlo calculations
Ryan Curry, Joel E. Lynn, Kevin E. Schmidt, and Alexandros Gezerlis
Author(s): Ryan Curry, Joel E. Lynn, Kevin E. Schmidt, and Alexandros Gezerlis

A technique that allows one to fuse nonperturbative many-body calculations and perturbative modern nuclear forces is reported on. The method was used to test some of the underlying assumptions of nuclear chiral forces and led to evidence that, at least in some regimes, they are violated.

[Phys. Rev. Research 5, L042021] Published Wed Nov 08, 2023

Found 1 papers in nat-comm

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

Emergence of Weyl fermions by ferrimagnetism in a noncentrosymmetric magnetic Weyl semimetal
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