Article
Materials Science, Multidisciplinary
Chuanshuai Huang, Yajun Wei, Yongchun Tao, Jun Wang
Summary: The study shows that by controlling the orientation of the exchange field, a 0-π transition can be achieved in graphene-based superconductor-ferromagnet-R-superconductor structures, while varying the RSOC strength λ does not directly affect this transition, but it is a necessary condition for the transition induced by changing the orientation.
Article
Materials Science, Multidisciplinary
W. Zeng, R. Shen
Summary: In this study, a method for generating transverse valley currents based on pure crossed Andreev reflection (pCAR) in hybrid junctions is proposed. The experimental results show that this method is highly efficient in charge-valley conversion and has potential applications in valleytronic devices.
Article
Materials Science, Multidisciplinary
Wei-Tao Lu, Qing-Feng Sun
Summary: In this study, subgap transport through AF/S and AF/S/AF junctions controlled by electric field in a buckled honeycomb system was investigated. The spin-valley polarized half-metallic phase and pure crossed Andreev reflection were achieved due to spin-orbit coupling, with the possibility of generating the pure CAR without AR and EC. A spin-valley switch effect could be realized by adjusting the electric field, and the properties of AR and CAR processes strongly depended on the spin-valley polarized states. The device could potentially be used for electrical measurement of the CAR process and spin-valley switch.
Article
Materials Science, Multidisciplinary
Lu Gao, Qiang Cheng, Qing-Feng Sun
Summary: In this study, we investigate the Andreev reflections and quantum transport in the proximitized graphene/superconductor junction. We find that the presence of pseudospin staggered potential and intrinsic spin-orbit coupling in the junction leads to spin-valley dependent double Andreev reflections and anomalous transport properties. These spin-valley dependent Andreev reflections offer a way to detect the induced potential and coupling in graphene and establish the foundation of superconductor electronics based on spin-valley indices.
Article
Physics, Multidisciplinary
Hong Li, Xin-Jian Yang
Summary: The spin-dependent Andreev reflection in a thin-film topological insulator ferromagnet/superconductor junction is investigated theoretically. It is found that the magnetic gap in the ferromagnet enhances the Andreev retro-reflection while suppressing the specular Andreev reflection. Applying a gate potential to the electrode on top of the superconductor enhances both types of reflections.
Article
Physics, Applied
Tobias W. Schmitt, Benedikt Frohn, Wilhelm Wittl, Abdur R. Jalil, Michael Schleenvoigt, Erik Zimmermann, Anne Schmidt, Thomas Schaepers, Juan Carlos Cuevas, Alexander Brinkman, Detlev Gruetzmacher, Peter Schueffelgen
Summary: In this study, the temperature-dependent behavior of a Bi2Te3-based Josephson junction (JJ) with transparent interfaces is investigated, providing insights into the contributions of bulk and surface states in topological insulator JJs. Differential conductance spectra of multiple Andreev reflections (MARs) are measured in electrical transport experiments, showing a qualitative temperature-dependent change from peak features to dip features. The observation of both types of MAR patterns in a single JJ suggests the presence of diffusive bulk and ballistic surface states, and their connection to the temperature dependence of the critical current. This work advances the understanding of induced superconductivity in topological insulators and offers new avenues for studying induced superconductivity in the topological surface states of these materials.
SUPERCONDUCTOR SCIENCE & TECHNOLOGY
(2023)
Article
Nanoscience & Nanotechnology
Jiahao Han, Luqiao Liu
Summary: This paper summarizes the methods for calibrating the charge-spin conversion efficiency in topological insulators and highlights their superiority as spin-orbit torque generators. Additionally, it reviews the results of magnetic switching under reduced current density in topological insulator/ferromagnet heterostructures.
Article
Materials Science, Multidisciplinary
Wei-Tao Lu, Qing-Feng Sun, Qiang Cheng
Summary: We studied the subgap transport in a ferromagnet/Ising superconductor/ferromagnet junction and found that the crossed Andreev reflection (CAR) and local Andreev reflection (LAR) strongly depend on the spin-polarized ferromagnet, magnetization direction, and Ising superconducting phase. For the same magnetization directions, equal-spin CAR can occur due to the spin-flip mechanism induced by the Ising spin-orbit coupling and equal-spin-triplet pairing. Both equal-spin CAR and equal-spin LAR show remarkable magnetoanisotropy with a period of pi and oscillatory behavior with chemical potential. The equal-spin CAR is more prominent with half-metal ferromagnet and double-band Ising superconductor while normal CAR is completely suppressed. In the case of different magnetization directions, oblique-spin CAR occurs with a magnetoanisotropic period of 2pi. The oblique-spin CAR process involves spins of the electron and hole that are neither parallel nor antiparallel. Furthermore, the property of oblique-spin CAR is very sensitive to the spin and valley degrees of freedom. Spin- and valley-polarized CAR can be achieved and controlled by the chemical potentials and magnetization directions.
Article
Physics, Applied
Xue Yang, Pablo Burset, Bo Lu
Summary: In a four-terminal setup, researchers found that a quantum spin Hall strip with different edges contacted by s-wave superconductors can exhibit Majorana bound states protected by time-reversal symmetry. They observed a subharmonic gap structure in the conductance peaks from multiple Andreev reflections, which is sensitive to the phase difference between the superconductors. This phase difference also controls an even-odd effect, where odd spikes disappear and even spikes split when the Majorana states form or when the superconductors have different gap sizes.
SUPERCONDUCTOR SCIENCE & TECHNOLOGY
(2023)
Article
Materials Science, Multidisciplinary
Rak-Hee Kim, Nam-Hee Kim, Bongkeon Kim, Yasen Hou, Dong Yu, Yong-Joo Doh
Summary: Superconducting proximity junctions made of topological insulator nanoribbons offer a useful platform for studying topological superconductivity. In this study, Josephson junctions using Sb-doped Bi2Se3 nanoribbons in contact with Al electrodes were fabricated and measured. The observations of Aharonov-Bohm and Altshuler-Aronov-Spivak oscillations in the axial magneto-conductance of the nanoribbons indicate the presence of metallic surface states.
CURRENT APPLIED PHYSICS
(2022)
Article
Chemistry, Multidisciplinary
Federico Binda, Stefano Fedel, Santos Francisco Alvarado, Paul Noel, Pietro Gambardella
Summary: The study investigates the spin-orbit torques (SOTs) and spin Hall magnetoresistance generated by Bi0.9Sb0.1(0001) when coupled with FeCo, confirming its effectiveness as a spin-injector material. The research finds that charge-to-spin conversion in single-crystal Bi0.9Sb0.1(0001) is isotropic despite the strong anisotropy of the topological surface states. Additionally, the damping-like SOT displays non-monotonic temperature dependence, with a minimum occurring at 20 K.
ADVANCED MATERIALS
(2023)
Article
Chemistry, Physical
Vsevolod Borovkov
Summary: A novel experimental approach is proposed to study spin-correlated polaron pairs on conjugated polymer molecules, with the migration, recombination, and evolution of the spin state of the pairs monitored at nanosecond resolution by observing recombination fluorescence under different magnetic fields.
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
(2021)
Article
Materials Science, Multidisciplinary
Peng Xu, Tian-Shu Deng
Summary: Researchers propose and study a solvable spin chain model by mapping it to a Floquet superconductor through the Jordan-Wigner transformation, to understand the rigidity and robustness of the discrete time crystal (DTC) phase. The phase diagrams of Floquet topological systems are characterized by topological invariants and indicate the existence of anomalous edge states. The subharmonic oscillation, a typical signal of DTC, can be generated from these edge states and protected by topology and solvability. The robustness of DTC is also examined by adding symmetry-preserving and symmetry-breaking perturbations, providing a deep understanding of DTC when applied to other interacting or dissipative systems.
Article
Engineering, Electrical & Electronic
Reza Daqiq
Summary: This study investigates spin-polarized currents in symmetric and asymmetric resonant magnetic tunnel junctions with a non-magnetic metal layer. It is found that a full spin polarization can be achieved by adjusting the thickness of the non-magnetic metal layer. Asymmetric junctions show higher charge and spin currents compared to symmetric junctions, suggesting potential use in new spin-filter devices for spintronics applications.
JOURNAL OF ELECTRONIC MATERIALS
(2021)
Article
Physics, Multidisciplinary
Dunkan Martinez, Alvaro Diaz-Fernandez, Pedro A. Orellana, Francisco Dominguez-Adame
Summary: Topological superconductors are promising candidates for the search of Majorana zero modes, which are important for quantum computation. It is necessary to study the behavior of electron states in topological superconductors in the presence of magnetic or non-magnetic impurities. The focus is on scattering resonances and spin texture to understand the spin behavior of the electrons. The results show evidence of topological robustness with scattering resonances outside the superconducting gap. Non-trivial and anisotropic spin textures related to the Dzyaloshinskii-Moriya interaction are also discovered, indicating a Ruderman-Kittel-Kasuya-Yosida interaction controlled by Friedel oscillations. These findings are valuable for further investigations on many-point-impurity scattering or impurity potentials with finite range.
ANNALEN DER PHYSIK
(2023)
Article
Physics, Multidisciplinary
Wen-Yu He, Xiao Yan Xu, K. T. Law
Summary: Kramers-Weyl semimetals, with a chiral crystal structure, exhibit a strong longitudinal magnetoelectric response, making them potential candidates for magnetic switching in ferromagnetic systems. This unique material property arises from the chiral lattice symmetry, allowing for new designs of spin-orbit torque devices with electric control of magnetization switching.
COMMUNICATIONS PHYSICS
(2021)
Article
Physics, Multidisciplinary
James Jun He, Yukio Tanaka, Naoto Nagaosa
Summary: Majorana fermions, as charge-neutral quasiparticles, exist on the boundaries of two-dimensional topological superconductors and generate enhanced local optical response. The features of local optical conductivity of chiral Majorana fermions distinguish them from trivial superconductors or insulators, as well as normal fermion edge states in quantum Hall systems. This provides a new applicable method to detect dispersive Majorana fermions and may lead to a novel direction in this research field.
PHYSICAL REVIEW LETTERS
(2021)
Article
Multidisciplinary Sciences
Chang-woo Cho, Jian Lyu, Cheuk Yin Ng, James Jun He, Kwan To Lo, Dmitriy Chareev, Tarob A. Abdel-Baset, Mahmoud Abdel-Hafiez, Rolf Lortz
Summary: The research reveals superconductivity beyond the Pauli limit in bulk single crystals of NbS2 under a precisely parallel field alignment, suggesting the development of a Fulde-Ferrell-Larkin-Ovchinnikov state.
NATURE COMMUNICATIONS
(2021)
Article
Physics, Multidisciplinary
Ying-Ming Xie, Cheng-Ping Zhang, Jin-Xin Hu, Kin Fai Mak, K. T. Law
Summary: Moire heterobilayer transition metal dichalcogenides (TMDs) are ideal for simulating the single-band Hubbard model and interesting correlated phases have been observed in these systems. Recent research has shown that topologically nontrivial states can be observed in heterobilayers, in which pseudomagnetic fields induced by lattice relaxation play a crucial role.
PHYSICAL REVIEW LETTERS
(2022)
Article
Physics, Multidisciplinary
Tao Liu, James Jun He, Zhongmin Yang, Franco Nori
Summary: This paper introduces a new type of higher-order topological semimetal with Weyl exceptional rings, supporting both surface and hinge Fermi arcs. Dissipative terms can induce topological phase transitions by coupling exceptional rings with opposite topological charges.
PHYSICAL REVIEW LETTERS
(2021)
Article
Physics, Multidisciplinary
James Jun He, Yukio Tanaka, Naoto Nagaosa
Summary: Nonreciprocal responses in noncentrosymmetric systems are an important fundamental issue, especially non-dissipative and coherent nonreciprocal transport. Recent research on superconductor diodes has advanced this field significantly. This study provides theoretical descriptions and design principles of superconductor diodes, including analytical relations between nonreciprocal critical currents and system parameters in Rashba spin-orbit coupled systems, as well as numerical calculations.
NEW JOURNAL OF PHYSICS
(2022)
Article
Multidisciplinary Sciences
Yong-Ju Hai, Ze Zhang, Hao Zheng, Liang Kong, Jiansheng Wu, Dapeng Yu
Summary: Topological order is a new quantum phase characterized by degenerate ground states, long-range entanglement, and anyons. This article explores how the fusion-braiding properties of anyons, characterized by R and F matrices, can be experimentally measured. By using boundary-bulk duality and anyon condensation, the R matrices can be determined by measuring the half braidings of boundary excitations, while the F matrices can be measured by comparing quantum states involving the fusion of three anyons in two different orders. Experimental measurements of R and F matrices were successfully obtained using a toric code model encoded in three- and four-qubit systems and NMR quantum computer technology. A protocol to uniquely identify topological orders by measuring the fingerprints of anyons was proposed and demonstrated in few-qubit systems.
NATIONAL SCIENCE REVIEW
(2023)
Article
Optics
Shaojie Yuan, Chuanpu Liu, Jilei Chen, Song Liu, Jin Lan, Haiming Yu, Jiansheng Wu, Fei Yan, Jiang Xiao, Liang Jiang, Dapeng Yu
Summary: Recent progress in quantum computing and simulation based on superconducting qubits has entered the noisy intermediate-scale quantum (NISQ) era. This article proposes a hybrid system consisting of superconducting qubits and a yttrium iron garnet (YIG) system as an alternative way to achieve coupling for quantum information processing. Numerical simulations demonstrate coherent transfer of quantum information between the flux qubit and the standing spin waves in YIG thin films.
Article
Materials Science, Multidisciplinary
Hongyu Ma, Ze Zhang, Pei-Hao Fu, Jiansheng Wu, Xiang -Long Yu
Summary: In this study, we extended the 2D SSH model by constructing different configurations and analyzed their electronic structures and topologies. We discovered several novel properties, including topologically protected edge states, metallic chains with different shapes, and a bulk-edge separation in a metal system. We also found a flat-band feature of topological edge states and explained its origin through the analysis of their spatial distribution.
Article
Optics
Ze Zhang, Xinyue Long, Xiuzhu Zhao, Zidong Lin, Kai Tang, Hongfeng Liu, Xiaodong Yang, Xinfang Nie, Jiansheng Wu, Jun Li, Tao Xin, Keren Li, Dawei Lu
Summary: This paper proposes a method based on quantum scattering circuit to directly and efficiently measure the modular transformation matrix of topological orders. The method is successfully implemented in a nuclear magnetic resonance quantum simulator to simulate both Abelian and non-Abelian topological orders. This work opens up new possibilities for studying topological orders in circuit-based quantum simulators.
Article
Materials Science, Multidisciplinary
Xiang-Long Yu, Pei-Hao Fu, Jiansheng Wu
Summary: In this work, the authors studied the Kane-Mele model with next-nearest-neighbor Rashba spin-orbit coupling and investigated the topological effects of two-dimensional materials. They identified various phase transitions and proposed a scheme for designing a spin-resolved filter based on the real QSH material stanene.
Article
Physics, Multidisciplinary
Ying-Ming Xie, K. T. Law, Patrick A. Lee
Summary: The recent study discovered signatures of Majorana bound states in EuS/Au/superconductor heterostructures, with the formation mechanism explained using topological phase diagrams and scattering matrix methods. Chemical potential step and normal reflections are key factors for creating topological regimes, which exhibit periodic oscillations in size with variations in chemical potential and sample width. The ferromagnetic strip geometry is shown to have several advantages over other proposed quasi-one-dimensional schemes.
PHYSICAL REVIEW RESEARCH
(2021)
Article
Physics, Multidisciplinary
Wen-Yu He, K. T. Law
Summary: In this study, it was found that the current-induced orbital magnetoelectric effect in superconductors can induce significant orbital magnetization, with a noticeable change near the superconductor-normal metal phase transition. The proposed theory can be useful for detecting unconventional magnetoelectric effects in superconductors with nonuniform pairing, such as twisted bilayer graphene.
PHYSICAL REVIEW RESEARCH
(2021)
Article
Materials Science, Multidisciplinary
James Jun He, Naoto Nagaosa
Summary: Raman scattering in Majorana edge modes of Kitaev spin liquids and topological superconductors shows differences in energy spectra, with Kitaev spin liquids varying with omega(3) and topological superconductors exhibiting a gap.
Article
Materials Science, Multidisciplinary
Xiang-Long Yu, Jiansheng Wu
Summary: In this study, the effects of the Zeeman field on the Kane-Mele model were investigated. Two different types of quantum anomalous Hall insulators and a gap oscillation region were identified. The competition between the Zeeman field and the Rashba SOC leads to a quantum critical phenomenon, with the gap oscillation corresponding to a metal-insulator transition in the system.