Article
Multidisciplinary Sciences
Minkyung Kim, Zihao Wang, Yihao Yang, Hau Tian Teo, Junsuk Rho, Baile Zhang
Summary: Researchers have designed and demonstrated a 3D photonic topological insulator (PTI) that exhibits self-guided topological surface states without the need for additional confinement. By removing spin-orbit coupling, this PTI opens new possibilities for manipulating photons at the outer surface of photonic bandgap materials.
NATURE COMMUNICATIONS
(2022)
Article
Multidisciplinary Sciences
Martin Claassen, Lede Xian, Dante M. Kennes, Angel Rubio
Summary: The study predicts that twisted bilayers of ZrS2 with the group-IV metal Zr can form an emergent moire Kagome lattice with strong spin-orbit coupling, leading to novel topological quantum phases dominated by strong spin-orbit interactions. At small twist angles, ZrS2 heterostructures give rise to an emergent and twist-controlled moire Kagome lattice, combining geometric frustration and strong spin-orbit coupling to realize a moire quantum spin Hall insulator with highly controllable and nearly-dispersionless bands.
NATURE COMMUNICATIONS
(2022)
Article
Chemistry, Multidisciplinary
Gennady M. Gusev, Ze D. Kvon, Alexander D. Levin, Nikolay N. Mikhailov
Summary: The thermoelectric response of 80 nm-thick strained HgTe films in a three-dimensional topological insulator was experimentally studied. An ambipolar thermopower was observed, with the Fermi energy shifting from the conduction band to the valence band. The comparison between theory and experiment showed that the thermopower was mainly due to phonon drag contribution, and the Seebeck coefficient was modified in the region where 2D Dirac electrons coexisted with bulk hole states due to electron-hole scattering.
Article
Materials Science, Multidisciplinary
Jian-Hao Zhang
Summary: Coupled-wire constructions are used to construct crystalline higher-order topological superconductors (HOTSCs) in two-dimensional interacting fermionic systems. The authors demonstrate the presence of Majorana corner modes on the edge of two representative examples of HOTSCs. Furthermore, they investigate the quantum phase transitions between different phases of 2D HOTSCs by tuning the interwire coupling.
Article
Materials Science, Multidisciplinary
Johan Carlstrom
Summary: The study introduces a controllable and unbiased strong-coupling diagrammatic Monte Carlo technique applicable to a wide range of fermionic systems and spin models. This technique is based on Wick's theorem and a recursive procedure, and achieves nonperturbative calculation of all local physics. The resulting expansion is described by simple diagrammatic rules suitable for systematic treatment via stochastic sampling, with benchmarks showing excellent agreement.
Article
Chemistry, Multidisciplinary
Ioannis Thanopulos, Vassilios Yannopapas, Emmanuel Paspalakis
Summary: In this study, the spontaneous emission dynamics of a quantum emitter near a topological insulator Bi2Se3 spherical nanoparticle are investigated. High Purcell factors up to 1010 at large distances in the terahertz regime are observed using the electromagnetic Green's tensor method. The research shows non-Markovian spontaneous emission dynamics and potential dynamical quantum speedup for short vacuum decay times, while the dynamics become progressively Markovian and the quantum speedup vanishes as the vacuum decay times increase. Additionally, a hybrid bound state between the quantum emitter and the continuum of electromagnetic modes affected by the nanoparticle is observed.
Article
Optics
Denitsa Baykusheva, Alexis Chacon, Dasol Kim, Dong Eon Kim, David A. Reis, Shambhu Ghimire
Summary: The study investigates the strong-field regime of light-matter interactions in topological-insulators, focusing on high-order harmonic generation. A major difference is observed in harmonic yields between surface bands and bulk states, with the surface contribution showing a peak for circularly polarized fields. Anomalous behavior is attributed to enhanced interband dipole amplitude and circular Berry connections near the Dirac point, as well as higher-order hexagonal warping terms in the Hamiltonian.
Article
Materials Science, Multidisciplinary
Shoubhik Mandal, Debarghya Mallick, Abhishek Banerjee, R. Ganesan, P. S. Anil Kumar
Summary: We present magnetotransport measurements on Bi1Sb1Te1.5Se1.5/RuCl3 heterostructure nanodevices. The interplay between bulk and surface transport channels in Bi1Sb1Te1.5Se1.5 (BSTS) is observed through temperature-dependent resistivity measurements. The presence of topological surface states (TSS) and electrically coupled Rashba surface states (RSS) is indicated by the observed multichannel weak antilocalization effect and nonlinear Hall effect, supported by a two-band model and analysis using the Lu-Shen model.
Article
Materials Science, Multidisciplinary
Xiao-Tian Wang, Xue-Fang Dai, Hong-Ying Jia, Li-Ying Wang, Guo-Dong Liu, Xi-Feng Liu, Wen Yuan, Yu-Ting Cui
Summary: It is found that the topological insulating state can be achieved in quaternary Heusler compounds by strain engineering or element substitution. Most compounds investigated have a negative formation energy, suggesting they could be synthesized in reality.
Article
Materials Science, Multidisciplinary
Loredana M. Vasiloiu, Apoorv Tiwari, Jens H. Bardarson
Summary: This study investigates the coherence times of Majorana zero modes in different scenarios by explicitly computing their closed form expressions in models of various dimensional superconductors. The results show enhanced coherence times for a certain class of Majorana operators under specific dissipative dynamics, while the coherence of the remaining operators decays much faster. Additionally, the numerical simulations demonstrate the robustness of the coherence times to the presence of disorder.
Article
Optics
Kai-Xin Hu, Chao Chen, Lu Qi, Wen-Xue Cui, Shou Zhang, Hong-Fu Wang
Summary: In this study, the topological phase transition and edge states in a quasi-three-dimensional topological system mapped by a circuit quantum electrodynamic lattice are investigated. The system undergoes a topological phase transition with increasing on-site potential strength, leading to changes in the number of Weyl points. Under open boundary conditions, the phase transition is reflected by energy band separation and the emergence of new edge states, including two pairs of crossed edge states in energy gaps at certain values of the periodic parameters. The edge states can be directly detected by measuring the average photon number of the cavity field in the steady state, benefiting from the Bose statistical properties of the circuit quantum electrodynamic.
Article
Materials Science, Multidisciplinary
Bin-Bin Ruan, Jun-Nan Sun, Yin Chen, Qing-Song Yang, Kang Zhao, Meng-Hu Zhou, Ya-Dong Gu, Ming-Wei Ma, Gen-Fu Chen, Lei Shan, Zhi-An Ren
Summary: By doping P into Mo5Si3, we discovered strong-coupling superconductivity in Mo5Si3-xPx. Mo5Si3 itself is not a superconductor, but upon P doping, Mo5Si3-xPx exhibits bulk superconductivity. Mo5Si1.5P1.5 has a Tc as high as 10.8 K, setting a new record among W5Si3-type superconductors. Mo5Si1.5P1.5 is a fully gapped superconductor with strong electron-phonon coupling.
SCIENCE CHINA-MATERIALS
(2022)
Review
Physics, Multidisciplinary
B. Q. Lv, T. Qian, H. Ding
Summary: Topological semimetals are characterized by bulk band crossings, which have led to increased research activities in the field due to precise theoretical predictions, well-controlled material synthesis, and advanced characterization techniques. The distinct features of these materials include dimensionality, degeneracy, slope and order of band dispersion, topological invariants, and crystallographic symmetries that stabilize band crossings. Additionally, the unique properties of various topological semimetal phases, such as nontrivial surface states and transport responses, have been reviewed.
REVIEWS OF MODERN PHYSICS
(2021)
Article
Materials Science, Multidisciplinary
Thais Chagas, Omar A. Ashour, Guilherme A. S. Ribeiro, Wendell S. Silva, Zhenglu Li, Steven G. Louie, Rogerio Magalhaes-Paniago, Yves Petroff
Summary: The electronic topology of Bi4Te3, composed of alternating Bi2 and Bi2Te3 layers, is investigated. It is found that there are three adjacent strong topological gaps with protected surface states within a 2-eV range of the Fermi level. Additionally, a surface-state Fermi surface with strong hexagonal warping is observed.
Article
Materials Science, Multidisciplinary
Jun Ho Son, S. Raghu
Summary: This study introduces a 3D network model for integer quantum Hall transition, demonstrating the existence of strong topological insulator phases. It also reveals a duality between weak topological phases and trivial insulator phases. Additionally, strong topological phases are shown to transition into a metallic phase under strong disorder.
Article
Physics, Applied
Akihiko Sekine, Kentaro Nomura
Summary: Axion electrodynamics in three-dimensional topological materials is characterized by a coupling between the axion and photon, resulting in fascinating magnetoelectric phenomena. This phenomenon is closely related to the topological magnetoelectric effect in such materials, involving static and dynamical axion insulators, as well as the electromagnetic responses of Weyl semimetals.
JOURNAL OF APPLIED PHYSICS
(2021)
Article
Astronomy & Astrophysics
Jan Schuette-Engel, David J. E. Marsh, Alexander J. Millar, Akihiko Sekine, Francesca Chadha-Day, Sebastian Hoof, Mazhar N. Ali, Kin Chung Fong, Edward Hardy, Libor Smejkal
Summary: It has been proposed that certain antiferromagnetic topological insulators may contain axion quasiparticles which can be used to detect axion dark matter. By calculating electromagnetic boundary conditions, transmission and reflection coefficients, a model is presented to measure resonant frequencies and damping coefficients of the material, confirming the existence of axion quasiparticles. The research shows that transmission spectroscopy can be used to achieve resonant conversion of axion dark matter into THz photons in a material volume independent of the resonant frequency.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2021)
Article
Physics, Multidisciplinary
Yasufumi Araki, Jin Watanabe, Kentaro Nomura
Summary: This study theoretically explores the electronic structure of a magnetic nodal-line state in a topological Dirac semimetal by introducing magnetism. It finds that the system can transition into either a Weyl semimetal or a nodal-line semimetal depending on certain factors, demonstrating zero modes with specific band structures at the boundary which are numerically verified.
JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN
(2021)
Article
Physics, Multidisciplinary
Daichi Kurebayashi, Yasufumi Araki, Kentaro Nomura
Summary: This study theoretically investigates current- and charge-induced spin torques in magnetic Weyl semimetals. The results show that current-induced spin torques and charge-induced spin torques originate from different physical mechanisms.
JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN
(2021)
Article
Physics, Multidisciplinary
Yasufumi Araki, Jun'ichi Ieda
Summary: The momentum-space topology of electrons under strong spin-orbit coupling contributes to the electrically induced torques exerted on magnetic textures insensitively to disorder or thermal fluctuation. A direct connection between band topology and torques is presented by classifying the whole torques phenomenologically. Additionally, torques can also emerge intrinsically from the anomalous velocity of electrons regardless of a nonequilibrium transport current.
PHYSICAL REVIEW LETTERS
(2021)
Article
Physics, Applied
Mari Ohfuchi, Akihiko Sekine, Manabu Ohtomo, Kenichi Kawaguchi
Summary: By studying the stripes and steps in bilayer WTe2, it has been found that stripes oriented along the x direction suppress the QSH states, while stripes and steps along the y direction maintain the QSH states. This finding is significant for the application of QSH states in WTe2.
APPLIED PHYSICS EXPRESS
(2022)
Article
Multidisciplinary Sciences
Michihiko Yamanouchi, Yasufumi Araki, Takaki Sakai, Tetsuya Uemura, Hiromichi Ohta, Jun'ichi Ieda
Summary: In a ferromagnetic Weyl metal, a large effective magnetic field exerted on a magnetic domain wall by current has been reported. The ratio of the effective magnetic field to current density shows a nonmonotonic temperature dependence and surpasses the ratios of conventional spin-transfer torques and spin-orbit torques. This enhancement is well described by the topological Hall torque, which is exerted on the domain wall by Weyl electrons emerging around Weyl points under an applied electric field. The ratio of the effective magnetic field arising from the topological Hall torque to current density is over one order of magnitude higher than that originating from spin-transfer torques and spin-orbit torques in metallic systems, indicating that the topological Hall torque may provide a more energy-efficient way to manipulate magnetization in spintronics devices.
Article
Physics, Multidisciplinary
Jin Watanabe, Yasufumi Araki, Koji Kobayashi, Akihiro Ozawa, Kentaro Nomura
Summary: In this study, we numerically investigated the magnetic orderings on the kagome lattice based on the tight-binding Hamiltonian of electrons. We found that the kagome lattice model can exhibit both ferromagnetic and noncollinear antiferromagnetic orderings depending on the electron filling. Additionally, the spin-orbit coupling plays a crucial role in stabilizing the noncollinear orderings.
JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN
(2022)
Article
Nanoscience & Nanotechnology
Mari Ohfuchi, Akihiko Sekine
Summary: We investigated the 2D lateral heterojunctions of monolayer 1T'-WTe2 and monolayer 2H-MoTe2 and found that the QSH states appear at the junctions, which could be applied in future topological quantum computation.
ACS APPLIED NANO MATERIALS
(2023)
Article
Physics, Applied
Akihiko Sekine, Manabu Ohtomo, Kenichi Kawaguchi, Mari Ohfuchi
Summary: In this study, the electronic structure of three-dimensional higher-order topological insulators in the presence of step edges is investigated theoretically. It is found that a 1D conducting state with a helical spin structure and linear dispersion near zero energy appears at the step edge and on the opposite surface. The existence of this conducting state can be understood by adding two different-sized independent blocks of 3D higher-order topological insulators. The location of the conducting state changes to the dip below the step edge when the electron hopping perpendicular to the step is strong.
JOURNAL OF APPLIED PHYSICS
(2023)
Article
Astronomy & Astrophysics
Daiki Suenaga, Yasufumi Araki, Kei Suzuki, Shigehiro Yasui
Summary: We propose a new mechanism for heavy-quark spin polarization in quark matter induced by the Kondo effect under an external magnetic field. Through coupling between light quarks and the magnetic field in quark matter, the HQSP is driven by the Kondo effect. The results show a significant increase in HQSP with the appearance of the Kondo effect, which can be tested in future sign-problem-free lattice simulations.
Article
Physics, Multidisciplinary
Yasufumi Araki, Takahiro Misawa, Kentaro Nomura
Summary: Theoretical proposal of long-range spin transport mediated by surface states of a topological Dirac semimetal. Experimental demonstration of robustness and long-range stability of the proposed scheme for spin transport.
PHYSICAL REVIEW RESEARCH
(2021)
Article
Astronomy & Astrophysics
Daiki Suenaga, Yasufumi Araki, Kei Suzuki, Shigehiro Yasui
Summary: The study reveals that the Kondo effect can catalyze the chiral separation effect in quark matter, with an enhancement observed particularly in the dynamical limit. The presence of heavy impurities plays a crucial role in the transport phenomena of light quarks induced by a magnetic field.
Article
Physics, Multidisciplinary
Yasufumi Araki, Daiki Suenaga, Kei Suzuki, Shigehiro Yasui
Summary: After hybridizing relativistic and nonrelativistic fermions, their spin-orbital crossed susceptibility is modified around the band hybridization point, leading to spin polarization of nonrelativistic fermions. These effects are enhanced under a dynamic magnetic field and can be realized in solids with slight breaking of crystalline symmetry or in quark matter with dilute heavy quarks strongly hybridized with light quarks.
PHYSICAL REVIEW RESEARCH
(2021)
Article
Physics, Multidisciplinary
Yasufumi Araki, Daiki Suenaga, Kei Suzuki, Shigehiro Yasui
Summary: Two different types of relativistic Kondo effects were investigated, with one involving heavy-impurity degrees of freedom and the other introducing heavy-fermion degrees of freedom through heavy-fermion effective theories. The dispersions near the Fermi surface are very similar in both cases, but they differ in structure at low momentum.
PHYSICAL REVIEW RESEARCH
(2021)
