Found 39 papers in cond-mat

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The Thermoelectric Effect and Its Natural Heavy Fermion Explanation in Twisted Bilayer and Trilayer Graphene
Dumitru C\u{a}lug\u{a}ru, Haoyu Hu, Rafael Luque Merino, Nicolas Regnault, Dmitri K. Efetov, B. Andrei Bernevig
arXiv:2402.14057v1 Announce Type: new Abstract: We study the interacting transport properties of twisted bilayer graphene (TBG) using the topological heavy-fermion (THF) model. In the THF model, TBG comprises localized, correlated $f$-electrons and itinerant, dispersive $c$-electrons. We focus on the Seebeck coefficient, which quantifies the voltage difference arising from a temperature gradient. We find that the TBG's Seebeck coefficient shows unconventional (strongly-interacting) traits: negative values with sawtooth oscillations at positive fillings, contrasting typical band-theory expectations. This behavior is naturally attributed to the presence of heavy (correlated, short-lived $f$-electrons) and light (dispersive, long-lived $c$-electrons) electronic bands. Their longer lifetime and stronger dispersion lead to a dominant transport contribution from the $c$-electrons. At positive integer fillings, the correlated TBG insulators feature $c$- ($f$-)electron bands on the electron (hole) doping side, leading to an overall negative Seebeck coefficient. Additionally, sawtooth oscillations occur around each integer filling due to gap openings. Our results highlight the essential importance of electron correlations in understanding the transport properties of TBG and, in particular, of the lifetime asymmetry between the two fermionic species (naturally captured by the THF model). Our findings are corroborated by new experiments in both twisted bilayer and trilayer graphene, and show the natural presence of strongly-correlated heavy and light carriers in the system.

Absence of localization in Weyl semimetals
Jinmin Yi, A. A. Burkov
arXiv:2402.14063v1 Announce Type: new Abstract: One of the fundamental facts of condensed matter physics is that sufficient amount of disorder always turns a Fermi liquid metal into an Anderson insulator: a compressible, but non-conducting phase of matter. Recently, topological semimetals have emerged as another way a metallic phase may be realized. In this paper we point out that, unlike ordinary metals, at least some topological semimetals are immune to localization, provided certain conditions are satisfied. We present several physical arguments, based on diagrammatic perturbation theory and Keldysh field theory, as well as domain wall network construction, to back up this claim.

On dualities of paired quantum Hall bilayer states at $\nu_T = \frac{1}{2} + \frac{1}{2}$
Luca R\"uegg, Gaurav Chaudhary, Robert-Jan Slager
arXiv:2402.14088v1 Announce Type: new Abstract: Density-balanced, widely separated quantum Hall bilayers at $\nu_T = 1$ can be described as two copies of composite Fermi liquids (CFLs). The two CFLs have interlayer weak-coupling BCS instabilities mediated by gauge fluctuations, the resulting pairing symmetry of which depends on the CFL hypothesis used. If both layers are described by the conventional Halperin-Lee-Read (HLR) theory-based composite electron liquid (CEL), the dominant pairing instability is in the $p+ip$ channel; whereas if one layer is described by CEL and the other by a composite hole liquid (CHL, in the sense of anti-HLR), the dominant pairing instability occurs in the $s$-wave channel. Using the Dirac composite fermion (CF) picture, we show that these two pairing channels can be mapped onto each other by particle-hole (PH) transformation. Furthermore, we derive the CHL theory as the non-relativistic limit of the PH-transformed massive Dirac CF theory. Finally, we prove that an effective topological field theory for the paired CEL-CHL in the weak-coupling limit is equivalent to the exciton condensate phase in the strong-coupling limit.

Nonlinear longitudinal current of band-geometric origin in wires of finite thickness
Robin Durand, Louis-Thomas Gendron, Th\'eo Nathaniel Dionne, Ion Garate
arXiv:2402.14112v1 Announce Type: new Abstract: The miniaturization of integrated circuits is facing an obstruction due to the escalating electrical resistivity of conventional copper interconnects. The underlying reason for this problem was unveiled by Fuchs and Sondheimer, who showed that thinner wires are more resistive because current-carrying electrons encounter the rough surfaces of the wire more frequently therein. Here, we present a generalization of the Fuchs-Sondheimer theory to Dirac and Weyl materials, which are candidates for next-generation interconnects. We predict a nonlinear longitudinal electric current originating from the combined action of the Berry curvature and non-specular surface-scattering.

Quantum state preparation of topological chiral spin liquids via Floquet engineering
Matthieu Mambrini, Didier Poilblanc
arXiv:2402.14141v1 Announce Type: new Abstract: In condensed matter, Chiral Spin Liquids (CSL) are quantum spin analogs of electronic Fractional Quantum Hall states (in the continuum) or Fractional Chern Insulators (on the lattice). As the latter, CSL are remarquable states of matter, exhibiting topological order and chiral edge modes. Preparing CSL on quantum simulators like cold atom platforms is still an open challenge. Here we propose a simple setup on a finite cluster of spin-1/2 located at the sites of a square lattice. Using a Resonating Valence Bond (RVB) non-chiral spin liquid as initial state on which fast time-modulations of strong nearest-neighbor Heisenberg couplings are applied, following different protocols (out-of-equilibrium quench or semi-adiabatic ramping of the drive), we show the slow emergence of such a CSL phase. An effective Floquet dynamics, obtained from a high-frequency Magnus expansion of the drive Hamiltonian, provides a very accurate and simple framework fully capturing the out-of-equilibrium dynamics. An analysis of the resulting prepared states in term of Projected Entangled Pair states gives further insights on the topological nature of the chiral phase. Finally, we discuss possible applications to quantum computing.

Inclined junction in monolayer graphene: A gateway toward tailoring valley polarization of Dirac fermions
Shrushti Tapar, Bhaskaran Muralidharan
arXiv:2402.14210v1 Announce Type: new Abstract: Generating discernible valley contrasts and segregating valley-indexed fermions in real space within graphene poses considerable challenges due to the isotropic transport within the continuum energy range for degenerate valleys. This study unveils an interesting finding: introducing valley contrast through anisotropic chiral transport in isotropic Dirac systems like graphene, achieved by implementing a tilted PN junction. The tilted junction shifts the angular spectrum to larger angles in accordance with the tilt angle. This modifies the pseudospin-conserved modes across the junction, resulting in valley-resolved chiral transport. This approach not only induces valley splitting within the real space but also preserves the remarkable mobility of fermions, offering distinct advantages over alternative strategies. The comprehensive analysis includes optimizing the experimental setup, scrutinizing factors such as the sequence of the doped region, and examining critical parameters like the tilt angle delta and transition width d across the junction. Surprisingly, an increased transition width enhances transmission, attributed to specular edge scattering. Importantly, the system remains resilient to Anderson short-range edge disorder. The broader implication lies in the transformative potential of inducing analogous anisotropic chiral transport behaviors in isotropic Dirac systems, resembling the characteristics of tilted Dirac-Weyl semimetals, by incorporating a tilted PNJ.

Irregular Bloch Zener oscillations in two-dimensional flat-band Dirac materials
Li-Li Ye, Ying-Cheng Lai
arXiv:2402.14243v1 Announce Type: new Abstract: When a static electrical field is applied to a two-dimensional (2D) Dirac material, Landau-Zener transition (LZT) and Bloch-Zener oscillations can occur. Employing alpha-T3 lattices as a paradigm for a broad class of 2D Dirac materials, we uncover two phenomena. First, due to the arbitrarily small energy gaps near a Dirac point that make it more likely for LZTs to occur than in other regions of the Brillouin zone, the distribution of differential LZT probability in the momentum space can form a complicated morphological pattern. Second, a change in the LZT morphology as induced by a mutual switching of the two distinct Dirac points can lead to irregular Bloch-Zener oscillations characterized by a non-smooth behavior in the time evolution of the electrical current density associated with the oscillation. These phenomena are due to mixed interference of quantum states in multiple bands modulated by the geometric and dynamic phases. We demonstrate that the adiabatic-impulse model describing Landau-Zener-Stuckelberg interferometry can be exploited to calculate the phases, due to the equivalence between the alpha-T3 lattice subject to a constant electrical field and strongly periodically driven two- or three-level systems. The degree of irregularity of Bloch-Zener oscillations can be harnessed by selecting the morphology pattern, which is potentially experimentally realizable.

Spin-dependent edge states in two-dimensional Dirac materials with a flat band
Li-Li Ye, Chen-Di Han, Ying-Cheng Lai
arXiv:2402.14248v1 Announce Type: new Abstract: The phenomenon of spin-dependent quantum scattering in two-dimensional (2D) pseudospin-1/2 Dirac materials leading to a relativistic quantum chimera was recently uncovered. We investigate spin-dependent Dirac electron optics in 2D pseudospin-1 Dirac materials, where the energy-band structure consists of a pair of Dirac cones and a flat band. In particular, with a suitable combination of external electric fields and a magnetic exchange field, electrons with a specific spin orientation (e.g., spin-down) can be trapped in a class of long-lived edge modes, generating resonant scattering. The spin-dependent edge states are a unique feature of flat-band Dirac materials and have no classical correspondence. However, electrons with the opposite spin (i.e., spin up) undergo conventional quantum scattering with a classical correspondence, which can be understood in the framework of Dirac electron optics. A consequence is that the spin-down electrons produce a large scattering probability with broad scattering angle distribution in both near- and far-field regions, while the spin-up electrons display the opposite behavior. Such characteristically different behaviors of the electrons with opposite spins lead to spin polarization that can be as high as nearly 100%.

Unexpected versatile electrical transport behaviors of ferromagnetic nickel films
Kai-Xuan Zhang, Hanshu Xu, Jihoon Keum, Xiangqi Wang, Meizhuang Liu, Zuxin Chen
arXiv:2402.14275v1 Announce Type: new Abstract: Perpendicular magnetic anisotropy (PMA) of magnets is paramount for electrically controlled spintronics due to their intrinsic potentials for higher memory density, scalability, thermal stability and endurance, surpassing an in-plane magnetic anisotropy (IMA). Nickel film is a long-lived fundamental element ferromagnet, yet its electrical transport behavior associated with magnetism has not been comprehensively studied, hindering corresponding spintronic applications exploiting nickel-based compounds. Here, we systematically investigate the highly versatile magnetism and corresponding transport behavior of nickel films. As the thickness reduces within the general thickness regime of a magnet layer for a memory device, the hardness of nickel films' ferromagnetic loop of anomalous Hall effect increases and then decreases, reflecting the magnetic transitions from IMA to PMA and back to IMA. Additionally, the square ferromagnetic loop changes from a hard to a soft one at rising temperatures, indicating a shift from PMA to IMA. Furthermore, we observe a butterfly magnetoresistance resulting from the anisotropic magnetoresistance effect, which evolves in conjunction with the thickness and temperature-dependent magnetic transformations as a complementary support. Our findings unveil the rich magnetic dynamics and most importantly settle down the most useful guiding information for current-driven spintronic applications based on nickel film: The hysteresis loop is squarest for the ~8 nm-thick nickel film, of highest hardness with Rxyr/Rxys~1 and minimum Hs-Hc, up to 125 K; otherwise, extra care should be taken for a different thickness or at a higher temperature.

Exact non-Hermitian mobility edges and robust flat bands in two-dimensional Lieb lattices with imaginary quasiperiodic potentials
Xiang-Ping Jiang, Weilei Zeng, Yayun Hu, Peng Liu
arXiv:2402.14370v1 Announce Type: new Abstract: The mobility edge (ME) is a critical energy delineates the boundary between extended and localized states within the energy spectrum, and it plays a crucial role in understanding the metal-insulator transition in disordered or quasiperiodic systems. While there have been extensive studies on MEs in one-dimensional non-Hermitian (NH) quasiperiodic lattices recently, the investigation of exact NH MEs in two-dimensional (2D) cases remains rare. In the present study, we introduce a 2D dissipative Lieb lattice (DLL) model with imaginary quasiperiodic potentials applied solely to the vertices of the Lieb lattice. By mapping this DLL model to the 2D NH Aubry-Andr{\'e}-Harper (AAH) model, we analytically derive the exact ME and find it associated with the absolute eigenenergies. We find that the eigenvalues of extended states are purely imaginary when the quasiperiodic potential is strong enough. Additionally, we demonstrate that the introduction of imaginary quasiperiodic potentials does not disrupt the flat bands inherent in the system. Finally, we propose a theoretical framework for realizing our model using the Lindblad master equation. Our results pave the way for further investigation of exact NH MEs and flat bands in 2D dissipative quasiperiodic systems.

Probing excitons with time-resolved momentum microscopy
Marcel ReutzelI. Physikalisches Institut, Georg-August-Universit\"at G\"ottingen, G\"ottingen, Germany, G. S. Matthijs JansenI. Physikalisches Institut, Georg-August-Universit\"at G\"ottingen, G\"ottingen, Germany, Stefan MathiasI. Physikalisches Institut, Georg-August-Universit\"at G\"ottingen, G\"ottingen, Germany, International Center for Advanced Studies of Energy Conversion
arXiv:2402.14394v1 Announce Type: new Abstract: Excitons -- two-particle correlated electron-hole pairs -- are the dominant low-energy optical excitation in the broad class of semiconductor materials, which range from classical silicon to perovskites, and from two-dimensional to organic materials. Recently, the study of excitons has been brought on a new level of detail by the application of photoemission momentum microscopy -- a technique that has dramatically extended the experimental capabilities of time- and angle-resolved photoemission spectroscopy (trARPES). Here, we review how the energy- and momentum-resolved photoelectron detection scheme enables direct access to the energy landscape of bright and dark excitons, and, more generally, to the momentum-coordinate of the exciton that is fundamental to its wavefunction. Focusing on two-dimensional materials and organic semiconductors as two tuneable platforms for exciton physics, we first discuss the typical photoemission fingerprint of excitons in momentum microscopy and highlight that is is possible to obtain information not only on the electron- but also hole-component of the former exciton. Second, we focus on the recent application of photoemission orbital tomography to such excitons, and discuss how this provides a unique access to the real-space properties of the exciton wavefunction. Throughout the review, we detail how studies performed on two-dimensional transition metal dichalcogenides and organic semiconductors lead to very similar conclusions, and, in this manner, highlight the strength of time-resolved momentum microscopy for the study of optical excitations in semiconductors.

Observation of Surface State Suppression in Magnetic Weyl Semimetal NdAlSi
Cong Li, Jianfeng Zhang, Hongxiong Liu, Wanyu Chen, Timur Kim, Youguo Shi, Tao Xiang, Oscar Tjernberg
arXiv:2402.14447v1 Announce Type: new Abstract: Understanding and mastering the control of surface states in topological materials are crucial steps for the development of future electronic devices and technologies that leverage the unique properties of these materials. Here, using angle-resolved photoemission spectroscopy, we provide a good case study of this by visualizing the electronic structure of a magnetic Weyl semimetal on both flat and uneven surfaces. Our observations reveal that the preparation of an uneven sample surface can effectively suppress all surface states in the Weyl semimetal NdAlSi, including topological surface Fermi arcs. This results in the observation of pure bulk states devoid of any Fermi energy shift. This discovery not only opens up a new avenue to directly study the pure bulk states of a Weyl semimetal using low photon energies in ARPES but also provides key insights into the control of the surface states in topological materials.

Robust 1D proximity superconductivity along graphene domain walls in the quantum Hall regime
Julien Barrier, Na Xin, Minsoo Kim, Roshan Krishna Kumar, P. Kumaravadivel, Lee Hague, E. Nguyen, A. I. Berdyugin, Christian Moulsdale, V. V. Enaldiev, J. R. Prance, F. H. L. Koppens, R. V. Gorbachev, K. Watanabe, T. Taniguchi, L. I. Glazman, I. V. Grigorieva, V. I. Fal'ko, A. K. Geim
arXiv:2402.14451v1 Announce Type: new Abstract: Extensive efforts have been undertaken to combine superconductivity and the quantum Hall effect so that Cooper-pair transport between superconducting electrodes in Josephson junctions is mediated by one-dimensional (1D) edge states. This interest has been motivated by prospects of finding new physics, including topologically-protected quasiparticles, but also extends into metrology and device applications. So far it has proven challenging to achieve detectable supercurrents through quantum Hall conductors. Here we show that domain walls in minimally twisted bilayer graphene support exceptionally robust proximity superconductivity in the quantum Hall regime, allowing Josephson junctions operational in fields close to the upper critical field of superconducting electrodes. The critical current is found to be non-oscillatory, practically unchanging over the entire range of quantizing fields, with its value being limited by the quantum conductance of ballistic strictly-1D electronic channels residing within the domain walls. The described system is unique in its ability to support Andreev bound states in high fields and offers many interesting directions for further exploration.

Pressure tunable magnetic skyrmion phase in Co8Zn8Mn4 single crystals
Zhun Li, Xinrun Mi, Xinming Wang, Jian Lyu, Na Su, Aifeng Wang, Yisheng Chai, Bao Yuan, Wanju Luo, Hui Cheng, Jianxiang Gao, Hongliang Wang, Lijie Hao, Mingquan He, Junying Shen, Young Sun, Xin Tong
arXiv:2402.14477v1 Announce Type: new Abstract: In a magnetic skyrmion phase, magnetic moments form vortex-like topological textures which are of both fundamental and industrial interests. In $\beta$-Mn-type Co-Zn-Mn alloys, chrial magnetic skyrmions emerge above room temperature, providing a unique system for studying the skrymion physics and exploring spintronics applications. However, the magnetic skyrmion phase is typically confined in a narrow and limited temperature ($T$) and magnetic field ($H$) range. Here, we demonstrate that hydrostatic pressure can expand the skyrmion phase in the $T-H$ phase diagram of single-crystalline Co$_8$Zn$_8$Mn$_4$. At ambient pressure, signatures of skyrmions are seen within $T\sim302-308$ K and $H\sim50-100$ Oe. Applying a moderate pressure of 6 kbar extends this range to $T\sim300-310$ K and $H\sim50-150$ Oe. However, further escalation of pressure to 10 kbar results in a slight contraction of the skyrmion phase. These findings underscore the sensitivity of the skyrmion phase in Co$_8$Zn$_8$Mn$_4$ to external pressures, and hint at the potential of strain engineering, particularly in $\beta$-Mn-type Co-Zn-Mn thin films, as a promising avenue to customize the skyrmion phase.

First-principle tight-binding approach to angle-resolved photoemission spectroscopy simulations: importance of light-matter gauge and ubiquitous interference effects
Yun Yen, Gian Parusa, Michael Sch\"uler
arXiv:2402.14496v1 Announce Type: new Abstract: Angle-resolved photoemission spectroscopy (ARPES) is one of the most powerful techniques to study the electronic structure of materials. To go beyond the paradigm of band mapping and extract aspects of the Bloch wave-functions, the intricate interplay of experimental geometry, crystal structure, and photon polarization needs to be understood. In this work we discuss several model approaches to computing ARPES signals in a unified fashion. While we represent the Bloch wave-functions by first-principle Wannier functions, we introduce different approximations to the final states and discuss the implications for the predictive power. We also introduce various light-matter gauges and explain the role of the inevitable breaking of gauge invariance.Finally, we benchmark the different models for the two-dimensional semiconductor WSe$_2$, known for its strong Berry curvature, orbital angular momentum (OAM), and nontrivial orbital texture. The models are compared based on their ability to simulate photoemission intensity and interpret circular dichroism in ARPES (CD-ARPES). We show that interference effects are crucial to understanding the circular dichroism, and explain their photon-energy dependence. Our in-depth analysis provides insights into the advantages and limitations of various model approaches in clarifying the complex interplay between experimental observables and underlying orbital texture in materials.

Bulk Boundary Paradox in the Surface Reconstructed Magnetic Weyl Semimetal NdAlSi
Cong Li, Jianfeng Zhang, Hongxiong Liu, Wanyu Chen, Guowei Liu, Hanbin Deng, Craig Polley, Balasubramanian Thiagarajan, Timur Kim, Jiaxin Yin, Youguo Shi, Tao Xiang, Oscar Tjernberg
arXiv:2402.14518v1 Announce Type: new Abstract: The bulk boundary correspondence in the context of Weyl semimetals is a fundamental topological principle that establishes a connection between the bulk properties of the material and the emergence of specific surface states. In Weyl semimetals, the bulk boundary correspondence is manifested by the presence of surface Fermi arcs connecting pairs of Weyl nodes with opposite chirality. Here we demonstrate that this bulk boundary correspondence is challenged in the case of the surface selectively reconstructed noncentrosymmetric magnetic Weyl semimetal NdAlSi. By comparing angle-resolved photoemission spectroscopy measurements with surface projected density functional theory calculations and scanning tunneling microscope measurements, the existence of surface selective spontaneous reconstruction is demonstrated. The surface reconstruction in NdAlSi not only leads to the reconstruction of the surface Fermi arcs, but also generates new surface Fermi arcs that do not connect corresponding Weyl nodes. This observation challenges the conventional view of the bulk boundary correspondence in Weyl semimetals.

Auxiliary Calculations for Graphene-Based Quantum Hall Arrays Using Partially Recursive Star-Mesh Transformations
Dominick S. Scaletta, Albert F. Rigosi
arXiv:2402.14520v1 Announce Type: new Abstract: A previous mathematical approach adopted for optimizing the number of total device elements required for obtaining high effective quantized resistances in graphene-based quantum Hall array devices (QHARS) has been further explored with partial recursion patterns. Designs would assume the use of epitaxial graphene elements, whose quantized Hall resistance at the {\nu}=2 plateau (R_H \approx 12906.4 \Ohm) becomes the building block for larger effective, quantized resistances. Auxiliary calculations suggest the importance of applying full recursions at least once to maximize the reduction of total QHARS elements needed for high resistances.

Shubnikov-de Haas oscillations of biaxial-strain-tuned superconductors in pulsed magnetic field up to 60 T
King Yau Yip, Lingfei Wang, Tsz Fung Poon, Kai Ham Yu, Siu Tung Lam, Kwing To Lai, John Singleton, Fedor F. Balakirev, Swee K. Goh
arXiv:2402.14534v1 Announce Type: new Abstract: Two-dimensional (2D) materials have gained increasing prominence not only in fundamental research but also in daily applications. However, to fully harness their potential, it is crucial to optimize their properties with an external parameter and track the electronic structure simultaneously. Magnetotransport over a wide magnetic field range is a powerful method to probe the electronic structure and, for metallic 2D materials, quantum oscillations superimposed on the transport signals encode Fermi surface parameters. In this manuscript, we utilize biaxial strain as an external tuning parameter and investigate the effects of strain on the electronic properties of two quasi-2D superconductors, MoTe$_2$ and RbV$_3$Sb$_5$, by measuring their magnetoresistance in pulsed magnetic fields up to 60 T. With a careful selection of insulating substrates, we demonstrate the possibility of both the compressive and tensile biaxial strain, imposed on MoTe$_2$ and RbV$_3$Sb$_5$, respectively. For both systems, the applied strain has led to superconducting critical temperature enhancement compared to their free-standing counterparts, proving the effectiveness of this biaxial strain method at cryogenic temperatures. Clear quantum oscillations in the magnetoresistance -- the Shubnikov-de Haas (SdH) effect -- are obtained in both samples. In strained MoTe$_2$, the magnetoresistance exhibits a nearly quadratic dependence on the magnetic field and remains non-saturating even at the highest field. Whereas in strained RbV$_3$Sb$_5$, two SdH frequencies showed a substantial enhancement in effective mass values, hinting at a possible enhancement of charge fluctuations. Our results demonstrate that combining biaxial strain and pulsed magnetic field paves the way for studying 2D materials under unprecedented conditions.

Scanning SQUID study of ferromagnetism and superconductivity in infinite-layer nickelates
Ruby A. Shi, Bai Yang Wang, Yusuke Iguchi, Motoki Osada, Kyuho Lee, Berit H. Goodge, Lena F. Kourkoutis, Harold Y. Hwang, Kathryn A. Moler
arXiv:2402.14559v1 Announce Type: new Abstract: Infinite-layer nickelates $R_{1-x}$Sr$_{x}$NiO$_{2}$ ($R$ = La, Pr, Nd) are a class of superconductors with structural similarities to cuprates. Although long-range antiferromagnetic order has not been observed for these materials, magnetic effects such as antiferromagnetic spin fluctuations and spin-glass behavior have been reported. Different experiments have drawn different conclusions about whether the pairing symmetry is $s$- or $d$ wave. In this paper, we applied a scanning superconducting quantum interference device (SQUID) to probe the magnetic behavior of film samples of three infinite-layer nickelates (La$_{0.85}$Sr$_{0.15}$NiO$_2$, Pr$_{0.8}$Sr$_{0.2}$NiO$_2$, and Nd$_{0.775}$Sr$_{0.225}$NiO$_2$) grown on SrTiO$_3$ (STO), each with a nominal thickness of 20 unit cells. In all three films, we observed a ferromagnetic background. We also measured the magnetic susceptibility above the superconducting critical temperature in Pr$_{0.8}$Sr$_{0.2}$NiO$_2$ and La$_{0.85}$Sr$_{0.15}$NiO$_2$ and identified a non-Curie-Weiss dynamic susceptibility. Both magnetic features are likely due to NiO$_x$ nanoparticles. Additionally, we investigated superconductivity in Pr$_{0.8}$Sr$_{0.2}$NiO$_2$ and Nd$_{0.775}$Sr$_{0.225}$NiO$_2$, which exhibited inhomogeneous diamagnetic screening. The superfluid density inferred from the diamagnetic susceptibility in relatively homogeneous regions shows $T$-linear behavior in both samples. Finally, we observed superconducting vortices in Nd$_{0.775}$Sr$_{0.225}$NiO$_2$. We determined a Pearl length of 330 $\upmu$m for Nd$_{0.775}$Sr$_{0.225}$NiO$_2$ at 300 mK both from the strength of the diamagnetism and from the size and shape of the vortices. These results highlight the importance of considering NiO$_x$ particles when interpreting experimental results for these films.

Local Manipulation of Skyrmion Lattice in Fe3GaTe2 at Room Temperature
Shuaizhao Jin, Zhan Wang, Shouzhe Dong, Yiting Wang, Kun Han, Guangcheng Wang, Zunyi Deng, Xingan Jiang, Ying Zhang, Houbing Huang, Jiawang Hong, Xiaolei Wang, Tianlong Xia, Sang-Wook Cheong, Xueyun Wang
arXiv:2402.14573v1 Announce Type: new Abstract: Motivated by advances in spintronic devices, an extensive exploration is underway to uncover materials that host topologically protected spin textures, exemplified by skyrmions. One critical challenge involved in the potential application of skyrmions in van der Waals (vdW) materials is the attainment and manipulation of skyrmions at room temperature. In this study, we report the creation of intrinsic skyrmion state in van der Waals ferromagnet Fe3GaTe2. By employing variable temperature magnetic force microscopy, the skyrmion lattice can be locally manipulated on Fe3GaTe2 flake. The ordering of skyrmion state is further analyzed. Our result suggest Fe3GaTe2 emerges as a highly promising contender for the realization of skyrmion-based layered spintronic memory devices.

Spin-dependent interactions in orbital-density-dependent functionals: non-collinear Koopmans spectral functionals
Antimo Marrazzo, Nicola Colonna
arXiv:2402.14575v1 Announce Type: new Abstract: The presence of spin-orbit coupling or non-collinear magnetic spin states can have dramatic effects on the ground-state and spectral properties of materials, in particular on the band structure. Here, we develop non-collinear Koopmans-compliant functionals based on Wannier functions and density-functional perturbation theory, targeting accurate spectral properties in the quasiparticle approximation. Our non-collinear Koopmans-compliant theory involves functionals of four-component orbitals densities, that can be obtained from the charge and spin-vector densities of Wannier functions. We validate our approach on three emblematic and diverse semiconductors where the effect of spin-orbit coupling goes from small to very large: the III-IV semiconductor GaAs, the transition-metal dichalcogenide WSe$_2$, and the cubic perovskite CsPbBr$_3$. The predicted band gaps are comparable in accuracy to state-of-the-art many-body perturbation theory and include spin-dependent interactions and screening effects that are missing in standard diagrammatic approaches based on the random phase approximation. While the inclusion of orbital- and spin-dependent interactions in many-body perturbation theory requires self-screening or vertex corrections, that emerges naturally in the Koopmans-functionals framework.

Tunable transport in bi-disperse porous materials with vascular structure
Olivier Vincent, Th\'eo Tassin, Erik J. Huber, Abraham D. Stroock
arXiv:2402.14628v1 Announce Type: new Abstract: We study transport in synthetic, bi-disperse porous structures, with arrays of microchannels interconnected by a nanoporous layer. These structures are inspired by the xylem tissue in vascular plants, in which sap water travels from the roots to the leaves to maintain hydration and carry micronutrients. We experimentally evaluate transport in three conditions: high pressure-driven flow, spontaneous imbibition, and transpiration-driven flow. The latter case resembles the situation in a living plant, where bulk liquid water is transported upwards in a metastable state (negative pressure), driven by evaporation in the leaves; here we report stable, transpiration-driven flows down to $\sim -15$ MPa of driving force. By varying the shape of the microchannels, we show that we can tune the rate of these transport processes in a predictable manner, using a simple analytical (effective medium) approach and numerical simulations of the flow field in the bi-disperse media. We also show that the spontaneous imbibition behavior of a single structure - with fixed geometry - can behave very differently depending on its preparation (filled with air, vs. evacuated), because of a dramatic change in the conductance of vapor in the microchannels; this change offers a second way to tune the rate of transport in bi-disperse, xylem-like structures, by switching between air-filled and evacuated states.

Engineering and Revealing Dirac Strings in Spinor Condensates
Gui-Sheng Xu, Mudit Jain, Xiang-Fa Zhou, Guang-Can Guo, Mustafa A. Amin, Han Pu, Zheng-Wei Zhou
arXiv:2402.14705v1 Announce Type: new Abstract: Artificial monopoles have been engineered in various systems, yet there has been no systematic study on the singular vector potentials associated with the monopole field. We show that the Dirac string, the line singularity of the vector potential, can be engineered, manipulated, and made manifest in a spinor atomic condensate. We elucidate the connection among spin, orbital degrees of freedom, and the artificial gauge, and reveal that there exists a mapping between the vortex filament and the Dirac string. We also devise a proposal where preparing initial spin states with relevant symmetries can result in different vortex patterns, revealing an underlying correspondence between the internal spin states and the spherical vortex structures. Such a mapping also leads to a new way of constructing monopole harmonics. Our observation provides significant insights in quantum matter possessing internal symmetries in curved spaces.

Dominant 1/3-filling Correlated Insulator States and Orbital Geometric Frustration in Twisted Bilayer Graphene
Haidong Tian, Emilio Codecido, Dan Mao, Kevin Zhang, Shi Che, Kenji Watanabe, Takashi Taniguchi, Dmitry Smirnov, Eun-Ah Kim, Marc Bockrath, Chun Ning Lau
arXiv:2402.14774v1 Announce Type: new Abstract: Geometric frustration is a phenomenon in a lattice system where not all interactions can be satisfied, the simplest example being antiferromagnetically coupled spins on a triangular lattice. Frustrated systems are characterized by their many nearly degenerate ground states, leading to non-trivial phases such as spin ice and spin liquids. To date most studies are on geometric frustration of spins; much less explored is orbital geometric frustration. For electrons in twisted bilayer graphene (tBLG) at denominator 3 fractional filling, Coulomb interactions and the Wannier orbital shapes are predicted to strongly constrain spatial charge ordering, leading to geometrically frustrated ground states that produce a new class of correlated insulators (CIs). Here we report the observation of dominant denominator 3 fractional filling insulating states in large angle tBLG; these states persist in magnetic fields and display magnetic ordering signatures and tripled unit cell reconstruction. These results are in agreement with a strong-coupling theory of symmetry-breaking of geometrically frustrated fractional states.

Optical properties of two dimensional Dirac Weyl materials with a flatband
Li-Li Ye, Chen-Di Han, Ying-Cheng Lai
arXiv:2402.14238v1 Announce Type: cross Abstract: The emergence of a flat band in Dirac-Weyl materials offers new possibilities for electronic transitions, leading to stronger interaction with light. As a result, the optical conductivity can be significantly enhanced in these flat-band materials as compared with graphene, making them potentially better candidates for optical sensing and modulation. Recently, a comprehensive theory for the optical conductivity of a spectrum of flat-band Dirac-Weyl materials has been developed, with explicit formulas for both the real and imaginary parts of the conductivity derived through two independent approaches. This Perspective offers a review of the development. An understanding of the optical properties of the flat-band Dirac-Weyl materials paves the way for optical device applications in the terahertz-frequency domain.

Voltage tunable sign inversion of magnetoresistance in van der Waals Fe3GeTe2/MoSe2/Fe3GeTe2 tunnel junctions
Shouguo Zhu, Hailong Lin, Wenkai Zhu, Weihao Li, Jing Zhang, Kaiyou Wang
arXiv:2402.14510v1 Announce Type: cross Abstract: The magnetic tunnel junctions (MTJ) based on van der Waals (vdW) materials possess atomically smooth interfaces with minimal element intermixing. This characteristic ensures that spin polarization is well maintained during transport, leading to the emergence of richer magnetoresistance behaviors. Here, using all 2D vdW MTJs based on magnetic metal Fe3GeTe2 and non-magnetic semiconductor MoSe2, we demonstrate that the magnitude and even sign of the magnetoresistance can be tuned by the applied voltage. The sign inversion of the magnetoresistance is observed in a wide temperature range below the Curie temperature. This tunable magnetoresistance sign may be attributed to the spin polarizations of the tunneling carriers and the band structure of the two ferromagnetic electrodes. Such robust electrical tunability of magnetoresistance extends the functionalities of low-dimensional spintronics and makes it more appealing for next-generation spintronics with all-vdW MTJs.

Magnon bands in pyrochlore slabs with Heisenberg exchange and anisotropies
V. V. Jyothis, Bibhabasu Patra, V. Ravi Chandra
arXiv:2210.03548v3 Announce Type: replace Abstract: The pyrochlore lattice is a versatile venue to probe the properties of magnetically ordered states induced or perturbed by anisotropic terms like the Dzyaloshinskii-Moriya interactions or single-ion anisotropy. Several such ordered states have been investigated recently as precursors of topological magnons and the associated surface states. In parallel, there has been recent progress in growing thin films of magnetic materials with this lattice structure along high symmetry directions of the lattice. In both cases, an account of the magnetic excitations of relevant Hamiltonians for finite slabs is a necessary step in the analysis of the physics of these systems. We study here magnon bands in the slab geometry for a class of spin models on the pyrochlore lattice with Heisenberg exchange, Dzyaloshinskii-Moriya interaction and spin-ice anisotropy. For a range of model parameters, for both ferromagnetic and antiferromagnetic exchange, we compute the classical ground states for different slab orientations and determine the spin wave excitations above them. We analyze the ferromagnetic splay phase, the all-in-all-out phase and a coplanar phase and evaluate magnon dispersions for slabs oriented perpendicular to the $[111]$, $[100]$ and $[110]$ directions. For all the phases considered, depending on the slab orientation, magnon band structures can be non-reciprocal and we highlight the differences in the three orientations from this point-of-view. Finally, we present details of the surface localized magnons for all the three slab orientations in the phases we study. For the ferromagnetic splay phase and the all-in-all-out phase we analyze surface states associated with point degeneracies or nodal lines in the bulk spectrum by computing the magnonic Berry curvature and Weyl charges or Chern numbers associated with it.

Symmetry protected topological phases under decoherence
Jong Yeon Lee, Yi-Zhuang You, Cenke Xu
arXiv:2210.16323v4 Announce Type: replace Abstract: We study ensembles described by density matrices with potentially nontrivial topological features. In particular, we study a class of symmetry protected topological (SPT) phases under various types of decoherence, which can drive a pure SPT state into a mixed state. We demonstrate that the system can still retain the nontrivial topological information from the SPT ground state even under decoherence. In the "doubled Hilbert space", we provide a general definition for symmetry protected topological ensemble (SPT ensemble), and the main quantity that we investigate is various types of (boundary) anomalies in the doubled Hilbert space. We show that the notion of the strange correlator, previously proposed to as a diagnosis for the SPT ground states, can be generalized to capture these anomalies in mixed-state density matrices. Using both exact calculations of the stabilizer Hamiltonians and field theory evaluations, we demonstrate that under decoherence the nontrivial features of the SPT state can persist in the two types of strange correlators: type-I and type-II. We show that the nontrivial type-I strange correlator corresponds to the presence of the SPT information that can be efficiently identified and utilized from experiments, such as for the purpose of preparing for long-range entangled states. The nontrivial type-II strange correlator encodes the full topological response of the decohered mixed state density matrix, i.e., the information about the presence of the SPT state before decoherence. Therefore, our work provides a unified framework to understand decohered SPT phases from the information-theoretic viewpoint.

Effect of initial microstructure on its evolution and $\alpha \rightarrow \omega$ phase transition in Zr under hydrostatic loading
K. K. Pandey, Valery I. Levitas, Changyong Park, Guoyin Shen
arXiv:2301.10475v2 Announce Type: replace Abstract: The first study of the effect of the initial microstructure on its evolution under hydrostatic compression before, during, and after the irreversible $\alpha\rightarrow\omega$ phase transformation and during pressure release in Zr using in situ x-ray diffraction is presented. Two samples were studied: one is plastically pre-deformed Zr with saturated hardness and the other is annealed. Phase transformation $\alpha\rightarrow\omega$ initiates at lower pressure for the pre-deformed sample but above volume fraction of $\omega$ Zr $c= 0.7$, a larger volume fraction is observed for the annealed sample. This implies that the general theory based on the proportionality between the athermal resistance to the transformation and the yield strength must be essentially advanced. The crystal domain size significantly reduces, and microstrain and dislocation density increase during loading for both $\alpha$ and $\omega$ phases in their single-phase regions. For the $\alpha$ phase, domain sizes are much smaller for prestrained Zr, while microstrain and dislocation densities are much higher. Despite the generally accepted concept that hydrostatic pressure does not cause plastic straining, it does and is estimated. The microstructure is not inherited during phase transformation. The significant evolution of the microstructure and its effect on phase transformation demonstrates that their postmortem evaluation does not represent the actual conditions during loading. A simple model for the initiation of the phase transformation involving microstrain is suggested. The results suggest that an extended experimental basis is required for the predictive models for the combined pressure-induced phase transformations and microstructure evolutions.

Experimental Evidence for Defect Tolerance in Pb-Halide Perovskites
Naga Prathibha JastiBar Ilan University, Weizmann Institute of Science, Igal LevineHelmholtz-Zentrum Berlin, Yishay FeldmanWeizmann Institute of Science, Gary HodesWeizmann Institute of Science, Sigalit AharonWeizmann Institute of Science, David CahenBar Ilan University, Weizmann Institute of Science
arXiv:2305.16017v4 Announce Type: replace Abstract: The term defect tolerance (DT) is used often to rationalize the exceptional optoelectronic properties of Halide Perovskites (HaPs) and their devices. Even though DT lacked direct experimental evidence, it became a "fact" in the field. DT in semiconductors implies that structural defects do not translate to electrical and optical effects (e.g., due to charge trapping), associated with such defects. We present the first direct experimental evidence for DT in Pb-HaPs by comparing the structural quality of 2-dimensional (2D), 2D-3D, and 3D Pb-iodide HaP crystals with their optoelectronic characteristics using high-sensitivity methods. Importantly, we get information from the materials' bulk, because we sample at least a few hundred nanometers, up to several micrometers, from the sample's surface, which allows for assessing intrinsic bulk (and not only surface-) properties of HaPs. The results point to DT in 3D, 2D-3D, and 2D Pb-HaPs. Overall, our data provide an experimental basis to rationalize DT in Pb-HaPs. These experiments and findings can guide the search for, and design of other materials with DT.

Imaginary phonon modes and phonon-mediated superconductivity in Y2C3
Niraj K. Nepal, Paul C. Canfield, Lin-Lin Wang
arXiv:2308.00201v3 Announce Type: replace Abstract: For Y$_2$C$_3$ with a superconducting critical temperature (T$_c$) $\sim$18 K, zone-center imaginary optical phonon modes have been found for the high-symmetry $I$-$43d$ structure due to C dimer wobbling motion and electronic instability from a flat band near Fermi energy. After lattice distortion to the more stable lowest symmetry $P1$ structure, these stabilized low-energy phonon modes with a mixed C and Y character carry a strong electron-phonon coupling to give arise to the observed sizable T$_c$. Our work shows that compounds with the calculated dynamical instability should not be simply excluded in high-throughput search for new phonon-mediated superconductors. Moreover, we have studied the phase stability of the $I$-$43d$ structure by calculating the enthalpy of different structural motifs of binary compounds containing group IV elements at the 2:3 composition and also exploring the energy landscapes via $ab$ $initio$ molecular dynamics near and out of the $I$-$43d$ structure. Our results show that the $I$-$43d$ type structures with C dimers are preferred in the low to medium pressure range. Because of the wobbling motion of the C dimers, there are many local energy minimums with degenerated energies. Thus, the ensemble average of many $I$-$43d$-distorted structures with C dimer wobbling motion at finite temperature still gives an overall $I$-$43d$ structure.

Thermodynamic transitions and topology of spin-triplet superconductivity: Application to UTe$_2$
Henrik S. R{\o}ising, Max Geier, Andreas Kreisel, Brian M. Andersen
arXiv:2311.06097v2 Announce Type: replace Abstract: The discovery of unconventional superconductivity in the heavy-fermion material UTe$_2$ has reinvigorated research of spin-triplet superconductivity. We perform a theoretical study of coupled two-component spin-triplet superconducting order parameters and their thermodynamic transitions into the superconducting state. With focus on the behavior of the temperature dependence of the specific heat capacity, we find that two-component time-reversal symmetry breaking superconducting order may feature vanishing or even negative secondary specific heat anomalies. The origin of this unusual specific heat behavior is tied to the non-unitarity of the composite order parameter. Additionally, we supply an analysis of the topological surface states associated with the different possible spin-triplet orders: single-component orders host Dirac Majorana surface states in addition to possible bulk nodes. A second component breaking time-reversal symmetry gaps these surface states producing chiral Majorana hinge modes. DFT+$U$ band-structure calculations support that these topological phases are realized in UTe$_2$ when introducing weak superconducting pairing. Our topological analysis suggests measurable signatures for surface-probe experiments to acquire further evidence of the superconducting pairing symmetry.

Signatures of Majorana Bound States in the Diffraction Patterns of Extended Superconductor-Topological Insulator-Superconductor Josephson Junctions
Guang Yue, Can Zhang, Erik D. Huemiller, Jessica H. Montone, Gilbert R. Arias, Drew G. Wild, Jered Y. Zhang, David R. Hamilton, Xiaoyu Yuan, Xiong Yao, Deepti Jain, Jisoo Moon, Maryam Salehi, Nikesh Koirala, Seongshik Oh, Dale J. Van Harlingen
arXiv:2311.16489v2 Announce Type: replace Abstract: In an extended superconductor-topological insulator-superconductor (S-TI-S) Josephson junction in a magnetic field, localized Majorana bound states (MBS) are predicted to exist at the cores of Josephson vortices where the local phase difference across the junction is an odd-multiple of $\pi$. These states contribute a supercurrent with a $4\pi$-periodic current-phase relation (CPR) that adds to the conventional $2\pi$-periodic sinusoidal CPR. In this work, we present a comprehensive experimental study of the critical current vs. applied magnetic field diffraction patterns of lateral Nb-Bi$_2$Se$_3$-Nb Josephson junctions. We compare our observations to a model of the Josephson dynamics in the S-TI-S junction system to explore what feature of MBS are, or are not, exhibited in these junctions. Consistent with the model, we find several distinct deviations from a Fraunhofer diffraction pattern that is expected for a uniform sin$({\phi})$ CPR. In particular, we observe abrupt changes in the diffraction pattern at applied magnetic fields in which the current-carrying localized MBS are expected to enter the junction, and a lifting of the odd-numbered nodes consistent with a $4\pi$-periodic sin$(\phi/2)$-component in the CPR. We also see that although the even-numbered nodes often remain fully-formed, we sometimes see deviations that are consistent with quasiparticle-induced fluctuations in the parity of the MBS pairs that encodes quantum information.

Reversal of Orbital Hall Conductivity and Emergence of Tunable Topological Quantum States in Orbital Hall Insulator
Shilei Ji, Chuye Quan, Ruijia Yao, Jianping Yang, Xing'ao Li
arXiv:2312.14181v2 Announce Type: replace Abstract: Recent findings indicate that orbital angular momentum (OAM) has the capability to induce the intrinsic orbital Hall effect (OHE), which is characterized by orbital Chern number in the orbital Hall insulator. Unlike the spin-polarized channel in Quantum anomalous Hall insulator, the OAM is valley-locked, posing challenges in manipulating the corresponding edge state. Here we demonstrate the sign-reversal orbital Chern number through strain engineering by combing the $k \cdot p$ model and first-principles calculation. Under the manipulation of strain, we observe the transfer of non-zero OAM from the valence band to the conduction band, aligning with the orbital contribution in the electronic structure. Our investigation reveals that electrons and holes with OAM exhibit opposing trajectories, resulting in a reversal of the orbital Hall conductivity. Furthermore, we explore the topological quantum state between the sign-reversible OHE.

Non-Abelian generalization of non-Hermitian quasicrystal: PT-symmetry breaking, localization, entanglement and topological transitions
Longwen Zhou
arXiv:2302.05710v3 Announce Type: replace-cross Abstract: Non-Hermitian quasicrystal forms a unique class of matter with symmetry-breaking, localization and topological transitions induced by gain and loss or nonreciprocal effects. In this work, we introduce a non-Abelian generalization of the non-Hermitian quasicrystal, in which the interplay between non-Hermitian effects and non-Abelian quasiperiodic potentials create mobility edges and rich transitions among extended, critical and localized phases. These generic features are demonstrated by investigating three non-Abelian variants of the non-Hermitian Aubry-Andr\'e-Harper model. A unified characterization is given to their spectrum, localization, entanglement and topological properties. Our findings thus add new members to the family of non-Hermitian quasicrystal and uncover unique physics that can be triggered by non-Abelian effects in non-Hermitian systems.

Atomic interferometer based on optical tweezers
Jonathan Nemirovsky, Rafi Weill, Ilan Meltzer, Yoav Sagi
arXiv:2308.07768v2 Announce Type: replace-cross Abstract: Atomic interferometers measure forces and acceleration with exceptional precision. The conventional approach to atomic interferometry is to launch an atomic cloud into a ballistic trajectory and perform the wave-packet splitting in momentum space by Raman transitions. This places severe constraints on the possible atomic trajectory, positioning accuracy and probing duration. Here, we propose and analyze a novel atomic interferometer that uses micro-optical traps (optical tweezers) to manipulate and control the motion of atoms. The new interferometer allows long probing time, sub micrometer positioning accuracy, and utmost flexibility in shaping of the atomic trajectory. The cornerstone of the tweezer interferometer are the coherent atomic splitting and combining schemes. We present two adiabatic schemes with two or three tweezers that are robust to experimental imperfections and work simultaneously with many vibrational states. The latter property allows for multi-atom interferometry in a single run. We also highlight the advantage of using fermionic atoms to obtain single-atom occupation of vibrational states and to eliminate mean-field shifts. We examine the impact of tweezer intensity noise and demonstrate that, when constrained by shot noise, the interferometer can achieve a relative accuracy better than $10^{-11}$ in measuring Earth's gravitational acceleration. The sub-micrometer resolution and extended measurement duration offer promising opportunities for exploring fundamental physical laws in new regimes. We discuss two applications well-suited for the unique capabilities of the tweezer interferometer: the measurement of gravitational forces and the study of Casimir-Polder forces between atoms and surfaces. Crucially, our proposed tweezer interferometer is within the reach of current technological capabilities.

Correlation-induced phase transitions and mobility edges in an interacting non-Hermitian quasicrystal
Tian Qian, Yongjian Gu, Longwen Zhou
arXiv:2310.01275v3 Announce Type: replace-cross Abstract: Non-Hermitian quasicrystal constitutes a unique class of disordered open system with PT-symmetry breaking, localization and topological triple phase transitions. In this work, we uncover the effect of quantum correlation on phase transitions and entanglement dynamics in non-Hermitian quasicrystals. Focusing on two interacting bosons in a Bose-Hubbard lattice with quasiperiodically modulated gain and loss, we find that the onsite interaction between bosons could drag the PT and localization transition thresholds towards weaker disorder regions compared with the noninteracting case. Moreover, the interaction facilitates the expansion of the critical point of a triple phase transition in the noninteracting system into a critical phase with mobility edges, whose domain could be flexibly controlled by tuning the interaction strength. Systematic analyses of the spectrum, inverse participation ratio, topological winding number, wavepacket dynamics and entanglement entropy lead to consistent predictions about the correlation-driven phases and transitions in our system. Our findings pave the way for further studies of the interplay between disorder and interaction in non-Hermitian quantum matter.

Local markers for crystalline topology
Alexander Cerjan, Terry A. Loring, Hermann Schulz-Baldes
arXiv:2310.01398v2 Announce Type: replace-cross Abstract: Over the last few years, crystalline topology has been used in photonic crystals to realize edge- and corner-localized states that enhance light-matter interactions for potential device applications. However, the band-theoretic approaches currently used to classify bulk topological crystalline phases cannot predict the existence, localization, or spectral isolation of any resulting boundary-localized modes. While interfaces between materials in different crystalline phases must have topological states at some energy, these states need not appear within the band gap, and thus may not be useful for applications. Here, we derive a class of local markers for identifying material topology due to crystalline symmetries, as well as a corresponding measure of topological protection. As our real-space-based approach is inherently local, it immediately reveals the existence and robustness of topological boundary-localized states, yielding a predictive framework for designing topological crystalline heterostructures. Beyond enabling the optimization of device geometries, we anticipate that our framework will also provide a route forward to deriving local markers for other classes of topology that are reliant upon spatial symmetries.

Gravitational effects in a superconducting film struck by a laser pulse
Giovanni A. Ummarino, Antonio Gallerati
arXiv:2401.17903v2 Announce Type: replace-cross Abstract: We study the local interaction of the gravitational field with a superfluid condensate. To this end, we exploit the Ginzburg-Landau formalism with generalized Maxwell fields. The analysis shows that a slight local alteration of the gravitational field in a thin superconducting film can be achieved by laser pulses with particular characteristics.

Found 13 papers in prb
Date of feed: Fri, 23 Feb 2024 04:17:01 GMT

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

Magneto-optical anisotropies of two-dimensional antiferromagnetic $M\mathrm{P}{X}_{3}$ from first principles
Miłosz Rybak, Paulo E. Faria Junior, Tomasz Woźniak, Pawel Scharoch, Jaroslav Fabian, and Magdalena Birowska
Author(s): Miłosz Rybak, Paulo E. Faria Junior, Tomasz Woźniak, Pawel Scharoch, Jaroslav Fabian, and Magdalena Birowska

Here we systematically investigate the impact of the spin direction on the electronic and optical properties of transition metal phosphorus trichalcogenides ($M\mathrm{P}{X}_{3}, M=\mathrm{Mn}$, Ni, Fe; $X=\mathrm{S}$, Se) exhibiting various antiferromagnetic arrangements within the 2D limit. Our an…

[Phys. Rev. B 109, 054426] Published Thu Feb 22, 2024

Thermodynamic transitions and topology of spin-triplet superconductivity: Application to ${\mathrm{UTe}}_{2}$
Henrik S. Røising, Max Geier, Andreas Kreisel, and Brian M. Andersen
Author(s): Henrik S. Røising, Max Geier, Andreas Kreisel, and Brian M. Andersen

The discovery of unconventional superconductivity in the heavy-fermion material ${\mathrm{UTe}}_{2}$ has reinvigorated research of spin-triplet superconductivity. We perform a theoretical study of coupled two-component spin-triplet superconducting order parameters and their thermodynamic transitions…

[Phys. Rev. B 109, 054521] Published Thu Feb 22, 2024

Field theory for the dynamics of the open $O(N)$ model
J. Lang, M. Buchhold, and S. Diehl
Author(s): J. Lang, M. Buchhold, and S. Diehl

A field theory approach for the nonequilibrium relaxation dynamics in open systems at late times is developed. In the absence of conservation laws, all excitations are subject to dissipation. Nevertheless, ordered stationary states satisfy Goldstone's theorem. It implies a vanishing damping rate at …

[Phys. Rev. B 109, 064310] Published Thu Feb 22, 2024

Impact of correlations on topology in the Kane-Mele model decorated with impurities
Jan Skolimowski, Wojciech Brzezicki, and Carmine Autieri
Author(s): Jan Skolimowski, Wojciech Brzezicki, and Carmine Autieri

We propose an effective model for the study of the interplay between correlation and topology by decorating the Kane-Mele model with a set of localized interacting orbitals hybridized to just one sublattice, breaking the inversion symmetry. We show that, in the time-reversal symmetric case, the inte…

[Phys. Rev. B 109, 075147] Published Thu Feb 22, 2024

Topological gap opening without symmetry breaking from dynamical quantum correlations
F. Paoletti, L. Fanfarillo, M. Capone, and A. Amaricci
Author(s): F. Paoletti, L. Fanfarillo, M. Capone, and A. Amaricci

Topological phase transitions are typically associated with the formation of gapless states. Spontaneous symmetry breaking can lead to a gap opening, thereby obliterating the topological nature of the system. Here we highlight a completely different destiny for a topological transition in the presen…

[Phys. Rev. B 109, 075148] Published Thu Feb 22, 2024

Electrical operation of hole spin qubits in planar MOS silicon quantum dots
Zhanning Wang, Abhikbrata Sarkar, S. D. Liles, Andre Saraiva, A. S. Dzurak, A. R. Hamilton, and Dimitrie Culcer
Author(s): Zhanning Wang, Abhikbrata Sarkar, S. D. Liles, Andre Saraiva, A. S. Dzurak, A. R. Hamilton, and Dimitrie Culcer

Silicon hole quantum dots have been the subject of considerable attention thanks to their strong spin-orbit coupling enabling electrical control, a feature that has been demonstrated in recent experiments combined with the prospects for scalable fabrication in CMOS (complementary metal-oxide-semicon…

[Phys. Rev. B 109, 075427] Published Thu Feb 22, 2024

Erratum: Casimir-Polder attraction and repulsion between nanoparticles and graphene in out-of-thermal-equilibrium conditions [Phys. Rev. B 105, 195430 (2022)]
G. L. Klimchitskaya, V. M. Mostepanenko, and O. Yu. Tsybin
Author(s): G. L. Klimchitskaya, V. M. Mostepanenko, and O. Yu. Tsybin
[Phys. Rev. B 109, 079901] Published Thu Feb 22, 2024

First-principles calculations of MoSeTe/WSeTe bilayers: Stability, phonons, electronic band offsets, and Rashba splitting
Hamid Mehdipour and Peter Kratzer
Author(s): Hamid Mehdipour and Peter Kratzer

Janus materials have attracted much interest due to their intrinsic electric dipole moment and Rashba band splitting. We show that, by building bilayers of MoSeTe and WSeTe with different chalcogen atom sequences and different stacking patterns, one can modulate the net dipole moment strength and th…

[Phys. Rev. B 109, 085425] Published Thu Feb 22, 2024

Fracton-elasticity duality on curved manifolds
Lazaros Tsaloukidis, José J. Fernández-Melgarejo, Javier Molina-Vilaplana, and Piotr Surówka
Author(s): Lazaros Tsaloukidis, José J. Fernández-Melgarejo, Javier Molina-Vilaplana, and Piotr Surówka

The mechanical properties of crystals on curved substrates mix elastic, geometric, and topological degrees of freedom. In order to elucidate the properties of such crystals, we formulate the low-energy effective action that combines metric degrees of freedom with displacement fields and defects. We …

[Phys. Rev. B 109, 085427] Published Thu Feb 22, 2024

Nonreciprocal coherent all-optical switching between magnetic multistates
T. Zalewski, V. A. Ozerov, A. Maziewski, I. Razdolski, and A. Stupakiewicz
Author(s): T. Zalewski, V. A. Ozerov, A. Maziewski, I. Razdolski, and A. Stupakiewicz

We present experimental and computational findings of the laser-induced nonreciprocal motion of magnetization during ultrafast photomagnetic switching in garnets. We found distinct coherent magnetization precession trajectories and switching times between four magnetization states, depending on both…

[Phys. Rev. B 109, L060303] Published Thu Feb 22, 2024

Anomalous Hall effect by chiral spin textures in the two-dimensional Luttinger model
Ryunosuke Terasawa and Hiroaki Ishizuka
Author(s): Ryunosuke Terasawa and Hiroaki Ishizuka

Long-range magnetic textures, such as magnetic skyrmions, give rise to rich transport properties in magnetic metals, such as the anomalous Hall effect related to spin chirality, aka topological Hall effect. In addition to the topological Hall effect, recent studies on noncentrosymmetric magnets have…

[Phys. Rev. B 109, L060407] Published Thu Feb 22, 2024

Spontaneous voltage peaks in superconducting Nb channels without engineered asymmetry
Shamashis Sengupta, Miguel Monteverde, Sara Loucif, Florian Pallier, Louis Dumoulin, and Claire Marrache-Kikuchi
Author(s): Shamashis Sengupta, Miguel Monteverde, Sara Loucif, Florian Pallier, Louis Dumoulin, and Claire Marrache-Kikuchi

Rectification effects in solid-state devices are a consequence of nonreciprocal transport properties. This phenomenon is usually observed in systems with broken inversion symmetry. In most instances, nonreciprocal transport arises in the presence of an applied magnetic field and the rectified signal…

[Phys. Rev. B 109, L060503] Published Thu Feb 22, 2024

Tunable unconventional integer quantum Hall effect in two-dimensional Dirac-Weyl systems
Y. J. Jin, Y. Xu, X. L. Xiao, Z. J. Chen, and H. Xu
Author(s): Y. J. Jin, Y. Xu, X. L. Xiao, Z. J. Chen, and H. Xu

Two-dimensional (2D) Dirac semimetals possess intriguing properties due to their low-energy excitations behaving like Dirac fermions. A hallmark of these materials is the unconventional integer quantum Hall effect (IQHE), originating from the quantized Berry phase of Dirac fermions. Herein, using sy…

[Phys. Rev. B 109, L081404] Published Thu Feb 22, 2024

Found 4 papers in prl
Date of feed: Fri, 23 Feb 2024 04:17:00 GMT

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

Edge State, Band Topology, and Time Boundary Effect in the Fine-Grained Categorization of Chern Insulators
H. C. Wu, H. S. Xu, L. C. Xie, and L. Jin
Author(s): H. C. Wu, H. S. Xu, L. C. Xie, and L. Jin

We predict novel topological phases with broken time-reversal symmetry supporting the coexistence of opposite chiral edge states, which are fundamentally different from the photonic spin-Hall, valley-Hall, and higher-order topological phases. We find a fine-grained categorization of Chern insulators…

[Phys. Rev. Lett. 132, 083801] Published Thu Feb 22, 2024

Modeling Temperature-Dependent Electron Thermal Diffuse Scattering via Machine-Learned Interatomic Potentials and Path-Integral Molecular Dynamics
Dennis S. Kim, Michael Xu, and James M. LeBeau
Author(s): Dennis S. Kim, Michael Xu, and James M. LeBeau

Electron thermal diffuse scattering is shown to be sensitive to subtle changes in atomic vibrations and shows promise in assessing lattice dynamics at nanometer resolution. Here, we demonstrate that machine-learned interatomic potentials (MLIPs) and path-integral molecular dynamics can accurately ca…

[Phys. Rev. Lett. 132, 086301] Published Thu Feb 22, 2024

Observation of Free-Boundary-Induced Chiral Anomaly Bulk States in Elastic Twisted Kagome Metamaterials
Zi-Dong Zhang, Ming-Hui Lu, and Yan-Feng Chen
Author(s): Zi-Dong Zhang, Ming-Hui Lu, and Yan-Feng Chen

Chiral anomaly bulk states (CABSs) can be realized by choosing appropriate boundary conditions in a finite-size waveguide composed of two-dimensional Dirac semimetals, which have unidirectional and robust transport similar to that of valley edge states. CABSs use almost all available guiding space, …

[Phys. Rev. Lett. 132, 086302] Published Thu Feb 22, 2024

Physical Properties of an Aperiodic Monotile with Graphene-like Features, Chirality, and Zero Modes
Justin Schirmann, Selma Franca, Felix Flicker, and Adolfo G. Grushin
Author(s): Justin Schirmann, Selma Franca, Felix Flicker, and Adolfo G. Grushin

The discovery of the Hat, an aperiodic monotile, has revealed novel mathematical aspects of aperiodic tilings. However, the physics of particles propagating in such a setting remains unexplored. In this work we study spectral and transport properties of a tight-binding model defined on the Hat. We f…

[Phys. Rev. Lett. 132, 086402] Published Thu Feb 22, 2024

Found 2 papers in pr_res
Date of feed: Fri, 23 Feb 2024 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)

Dispersive drumhead states in nodal-line semimetal junctions
Francesco Buccheri, Reinhold Egger, and Alessandro De Martino
Author(s): Francesco Buccheri, Reinhold Egger, and Alessandro De Martino

We consider a smooth interface between a topological nodal-line semimetal and a topologically trivial insulator (e.g., the vacuum) or another semimetal with a nodal ring of different radius. Using a low-energy effective Hamiltonian including only the two crossing bands, we show that these junctions …

[Phys. Rev. Research 6, 013193] Published Thu Feb 22, 2024

Improving power-grid systems via topological changes or how self-organized criticality can help power grids
Géza Ódor, István Papp, Kristóf Benedek, and Bálint Hartmann
Author(s): Géza Ódor, István Papp, Kristóf Benedek, and Bálint Hartmann

Cascade failures in power grids occur when the failure of one component or subsystem causes a chain reaction of failures in other components or subsystems, ultimately leading to a widespread blackout or outage. Controlling cascade failures on power grids is important for many reasons like economic i…

[Phys. Rev. Research 6, 013194] Published Thu Feb 22, 2024

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)

Hyperbolic photonic topological insulators
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Found 1 papers in adv-mater
Date of feed: Thu, 22 Feb 2024 08:29:15 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 Cu3BHT‐Graphene van der Waals Heterostructure with Strong Interlayer Coupling for Highly Efficient Photoinduced Charge Separation
Zhiyong Wang, Shuai Fu, Wenjie Zhang, Baokun Liang, Tsai‐Jung Liu, Mike Hambsch, Jonas F. Pöhls, Yufeng Wu, Jianjun Zhang, Tianshu Lan, Xiaodong Li, Haoyuan Qi, Miroslav Polozij, Stefan C. B. Mannsfeld, Ute Kaiser, Mischa Bonn, R. Thomas Weitz, Thomas Heine, Stuart S. P. Parkin, Hai I. Wang, Renhao Dong, Xinliang Feng
Advanced Materials, Accepted Article.