A5075981885- Quasicrystal Structures and Properties
- Physics of Superconductivity and Magnetism
- Rare-earth and actinide compounds
- Iron-based superconductors research
- Theoretical and Computational Physics
- Quantum and electron transport phenomena
- Advanced Condensed Matter Physics
- Quantum Computing Algorithms and Architecture
- Advanced Chemical Physics Studies
- Cold Atom Physics and Bose-Einstein Condensates
- Heusler alloys: electronic and magnetic properties
- Quantum Information and Cryptography
- 2D Materials and Applications
- Magnetic properties of thin films
- Corporate Taxation and Avoidance
- Quantum chaos and dynamical systems
- Quantum many-body systems
- Spectral Theory in Mathematical Physics
- Topological Materials and Phenomena
- Metallurgical Processes and Thermodynamics
- Microstructure and mechanical properties
- Quantum Mechanics and Applications
- Quantum, superfluid, helium dynamics
- Stochastic processes and statistical mechanics
- Magnetic and transport properties of perovskites and related materials
RIKEN Center for Emergent Matter Science
2017-2024
Osaka University
2022-2024
Okayama University of Science
2018-2022
Tama University
2018
Tokyo Institute of Technology
2012-2016
The thermoelectric effect is attracting a renewed interest as concept for energy harvesting technologies. Nanomaterials have been considered key to realize efficient conversions owing the low dimensional charge and phonon transports. In this regard, recently emerging two-dimensional materials could be promising candidates with novel functionalities. Here we report that FeSe ultrathin films, high-Tc superconductor (Tc; superconducting transition temperature), exhibit superior responses. With...
We study a possible superconductivity in quasiperiodic systems, by portraying the issue within attractive Hubbard model on Penrose lattice. Applying real-space dynamical mean-field theory to consisting of 4181 sites, we find superconducting phase at low temperatures. Reflecting nonperiodicity lattice, state exhibits an inhomogeneity. According type inhomogeneity, is categorized into three different regions which cross over each other. Among them, weak-coupling region spatially extended...
We study the one-band Hubbard model on honeycomb lattice using a combination of quantum Monte Carlo (QMC) simulations and static as well dynamical mean-field theory (DMFT). This is known to show phase transition between Dirac semimetal antiferromagnetic insulator. The aim this paper provide detailed comparison these approaches by computing properties, notably ground-state energy, single-particle gap, double occupancy, staggered magnetization, quantities such spectral function. At level,...
We numerically study the physical properties of quasiperiodic superconductors with aim understanding superconductivity in quasicrystals. Considering attractive Hubbard model on Penrose tiling as a simple theoretical model, we calculate various basic superconducting and find deviations from universal values Bardeen-Cooper-Schrieffer theory constant density-of-states approximation. In particular, that jump specific heat at transition is about 10%--20% smaller than value, consistent...
We study the extended Anderson model on two-dimensional Penrose lattice, combining real-space dynamical mean-field theory with noncrossing approximation. It is found that Coulomb repulsion between localized and conduction electrons does not induce a valence transition, but crossover Kondo mixed states in contrast to conventional periodic system. In mixed-valence region close crossover, nontrivial distributions appear, characteristic of demonstrating state coexists local certain sites. The...
Abstract Dan Shechtman's discovery of quasicrystals in 1982 introduced the scientific world to aperiodic crystals with unique rotational symmetries, redefining traditional crystallography. Although superconductivity related periodic approximants has since been observed, true bulk was confirmed only 2018. This recent opens a new horizon not for study correlated but more generally nontrivial spatial order. The theoretical understanding superconducting poses challenges due their lack...
We study electron correlations in the half-filled Hubbard model on a two-dimensional Penrose lattice. Applying real-space dynamical mean-field theory to large clusters, we discuss how low-temperature properties are affected by quasiperiodic structure. By calculating double occupancy and renormalization factor at each site, clarify existence of Mott transition. The spatially dependent characteristic geometrical structure is also addressed.
We theoretically study the real-space distribution of supercurrent that flows under a uniform vector potential in two-dimensional quasiperiodic structure. This is done by considering attractive Hubbard model on Ammann-Beenker structure and studying superconducting phase within Bogoliubov-de Gennes mean-field theory. Decomposing local into paramagnetic diamagnetic components, we numerically investigate their dependencies average electron density, temperature, angle applied potential. find...
We present a new open-source program, DCore, that implements dynamical mean-field theory (DMFT). DCore features user-friendly interface based on text and HDF5 files. It allows DMFT calculations of tight-binding models to be performed predefined lattices as well ab initio constructed by external density functional codes through the Wannier90 package. Furthermore, provides interfaces many advanced quantum impurity solvers such Monte Carlo exact diagonalization solvers. This paper details...
We propose introducing an extended Hubbard Hamiltonian derived via the ab initio downfolding method, which was originally formulated for periodic materials, toward efficient quantum computing of molecular electronic structure calculations. By utilizing this first-principles chemical systems can be coarse-grained by eliminating degrees freedom in higher energy space and reducing number terms electron repulsion integral from O(N4) to O(N2). Our approach is validated numerically on vertical...
Among iron chalcogenide superconductors, FeS can be viewed as a simple, highly compressed relative of FeSe without nematic phase and with weaker electronic correlations. Under pressure, however, the superconductivity stoichiometric disappears reappears, forming two domes. We perform structure spin fluctuation theory calculations for tetragonal in order to analyze nature superconducting parameter. In random approximation, we find gap function $d$-wave symmetry at ambient agreement several...
The recently discovered Fe-based superconductor (FeBS) ${\mathrm{LaFe}}_{2}{\mathrm{As}}_{2}$ seems to break away from an established pattern that doping FeBS beyond $0.2e/\mathrm{Fe}$ destroys superconductivity. has apparent of $0.5e$, yet superconducts at 12.1 K. Its Fermi surface bears no visual resemblance with the canonical fermiology. It also exhibits two phases, none magnetic and only one superconducting. We show difference between them nonetheless a origin, featuring disordered...
Three-component fermionic optical lattice systems are investigated in dynamical mean-field theory for the Hubbard model. Solving effective impurity model by means of continuous-time quantum Monte Carlo simulations Nambu formalism, we find that $s$-wave superfluid state proposed recently is indeed stabilized repulsively interacting case and appears along first-order phase boundary between metallic paired Mott states paramagnetic system. The BCS-BEC crossover three-component system also addressed.
Abstract We study the distribution of supercurrent in attractive Hubbard model on a periodic approximant Ammann-Beenker structure by means Bogoliubov-de Gennes (BdG) mean-field theory. first investigate spatial distributions electron density and superconducting order parameter find crossover between states with (i) extended, (ii) localized, (iii) short-ranged Cooper pairs, similar to previous results Penrose tiling. Furthermore, we formulate expression for terms eigenenergies wave functions...
We study the attractive Hubbard model with mass imbalance to clarify low-temperature properties of fermionic mixtures in an optical lattice. By combining dynamical mean-field theory continuous-time quantum Monte Carlo simulation, we discuss competition between superfluid and density wave states at half filling. calculating energy order parameter for each state, that coexisting (supersolid) where are degenerate, is realized system. then determine phase diagram finite temperatures.
The spin-dependent band structure of CoS$_2$ which is a candidate for half-metallic ferromagnet was investigated by both spin- and angle-resolved photoemission spectroscopy theoretical calculations, in order to reappraise the half-metallicity electronic correlations. We determined three-dimensional Fermi surface structure. As result, we found that part minority spin bands on occupied side vicinity level, providing spectroscopic evidence not but very close half-metal. Band calculations using...
Quantum computers (QCs), which work based on the law of quantum mechanics, are expected to be faster than classical in several computational tasks such as prime factoring and simulation many-body systems. In last decade, research development QCs have rapidly advanced. Now hundreds physical qubits at our disposal, one can find remarkable experiments actually outperforming computer a specific task. On other hand, it is unclear what typical usages are. Here we conduct an extensive survey papers...
We study a two-dimensional Hubbard model on Penrose lattice by means of the real-space dynamical mean-field theory. Calculating renormalization factor and density states at each site, we discuss local electron correlations quasi-periodic structure. It is found that renormalized metallic state appears near Mott transition in system. also address spatially-dependent characteristic lattice.
We study the effect of carrier doping to Mott insulator on Penrose tiling, aiming at clarifying interplay between quasiperiodicity and strong electron correlations. numerically solve Hubbard model Penrose-tiling structure within a real-space dynamical mean-field theory, which can deal with singular self-energy necessary describe spatial inhomogeneity. find that correlation produces charge distribution unreachable by static approximation. In small region, spectrum shows site-dependent gap...
We develop a real-space extension of the dual fermion approach. This method is formulated in terms Green's functions and local vertex functions, which enables us to discuss nonlocal correlations inhomogeneous systems with an arbitrary geometric structure. first demonstrate that approach gives reasonable results for homogenous periodic system by taking into account onsite nearest-neighbor intersite correlations. Moreover, we study half-filled Hubbard model on quasiperiodic Penrose lattice...
The van-der-Waals gap of iron chalcogenide superconductors can be intercalated with a variety inorganic and organic compounds that modify the electron doping level layers. In ${\mathrm{Li}}_{x}{({\mathrm{C}}_{3}{\mathrm{N}}_{2}{\mathrm{H}}_{10})}_{0.37}\mathrm{FeSe}$, dome in superconducting transition temperature ${T}_{c}$ has been reported to occur range $x=0.06$ $x=0.68$. We use combination density functional theory spin fluctuation capture evolution temperatures theoretically. clearly...
We study intersite electron correlations in the half-filled Hubbard model on square lattices with periodic and open boundary conditions by means of a real-space dual fermion approach. By calculating renormalization factors, we clarify that nearest-neighbor already significantly reduce critical interaction. The Mott transition occurs at U/t ∼ 6.4, where U is interaction strength t hopping integral. This value consistent quantum Monte Carlo results. It shows importance short-range...