A5068173013- Physics of Superconductivity and Magnetism
- Advanced Condensed Matter Physics
- Quantum and electron transport phenomena
- Radical Photochemical Reactions
- Fluorine in Organic Chemistry
- Quantum many-body systems
- Quantum Information and Cryptography
- Organic and Molecular Conductors Research
- Cold Atom Physics and Bose-Einstein Condensates
- Topological Materials and Phenomena
- Quantum Computing Algorithms and Architecture
- Oxidative Organic Chemistry Reactions
- Advanced Chemical Physics Studies
- Graphene research and applications
- Iron-based superconductors research
- Magnetic and transport properties of perovskites and related materials
- Microstructure and Mechanical Properties of Steels
- High Temperature Alloys and Creep
- Quantum, superfluid, helium dynamics
- Synthesis of Organic Compounds
- Electronic and Structural Properties of Oxides
- 2D Materials and Applications
- Synthesis and Reactions of Organic Compounds
- Catalytic C–H Functionalization Methods
- Advanced Thermodynamics and Statistical Mechanics
RIKEN Center for Quantum Computing
2022-2025
RIKEN Center for Advanced Photonics
2025
Computing Center
2024
RIKEN Center for Emergent Matter Science
2020-2023
Scuola Internazionale Superiore di Studi Avanzati
2018-2019
RIKEN Center for Computational Science
2016-2019
RIKEN
2014-2019
Pioneer (Japan)
2018-2019
Chiba University
2009-2014
Health Sciences University of Hokkaido
1998-2004
We show that finite temperature variational cluster approximation (VCA) calculations on an extended Falicov-Kimball model can reproduce angle-resolved photoemission spectroscopy (ARPES) results ${\mathrm{Ta}}_{2}{\mathrm{NiSe}}_{5}$ across a semiconductor-to-semiconductor structural phase transition at 325 K. demonstrate the characteristic dependence of flat-top valence band observed by ARPES is reproduced VCA calculation realistic for excitonic insulator only when strong fluctuation taken...
We propose a scheme to restore spatial symmetry of Hamiltonian in the variational-quantum-eigensolver (VQE) algorithm for which quantum circuit structures used usually break symmetry. The symmetry-adapted VQE introduced here simply applies projection operator, is Hermitian but not unitary, desired irreducible representation group. entanglement state still represented nonunitarity operator treated classically as postprocessing framework. By numerical simulations spin-$1/2$ Heisenberg model on...
We study the spontaneous symmetry breaking of excitonic insulator state induced by Coulomb interaction $U$ in two-dimensional extended Falicov-Kimball model. Using variational cluster approximation (VCA) and Hartree-Fock (HFA), we evaluate order parameter, single-particle excitation gap, momentum distribution functions, coherence length excitons, anomalous spectra as functions at zero temperature. find that weak-to-intermediate coupling regime, Fermi surface plays an essential role...
Abstract The electron–electron and electron–phonon interactions play an important role in correlated materials, being key features for spin, charge pair correlations. Thus, here we investigate their effects strongly systems by performing unbiased quantum Monte Carlo simulations the square lattice Hubbard-Holstein model at half-filling. We study competition interplay between antiferromagnetism (AFM) charge-density wave (CDW), establishing its very rich phase diagram. In region AFM CDW phases,...
The variational cluster approximation is used to study the spontaneous symmetry breaking of excitonic insulator (EI) state in two-orbital Hubbard model defined on two-dimensional square lattice. Evaluating order parameter EI state, staggered magnetization, and number particles each orbital, we obtain ground-state phase diagram a wide space intra interorbital Coulomb interactions. We also calculate single-particle anomalous Green's functions. show that normal metallic unstable formation...
RIKEN covers fundamental research on physics, chemistry, biology, life and medical science, information mathematical engineering. Here, we outline activities quantum materials technology that include topological correlated materials, spintronics, nanoscale structures, atomic optics, computing.
To clarify the origin of a charge-density wave (CDW) phase in $1T\ensuremath{-}{\mathrm{TiSe}}_{2}$, we study ground-state property half-filled two-band Hubbard model triangular lattice including electron-phonon interaction. By using variational Monte Carlo method, electronic and degrees freedom are both treated quantum mechanically on an equal footing beyond mean-field approximation. We find that cooperation between Coulomb interaction is essential to induce CDW phase. show ``pure'' exciton...
The phase diagram of isotropically expanded graphene cannot be correctly predicted by ignoring either electron correlations, or mobile carbons, the effect applied stress, as was done so far. We calculate ground state enthalpy (not just energy) strained an accurate off-lattice Quantum Monte Carlo (QMC) correlated ansatz great variational flexibility. Following undistorted semimetallic (SEM) at low strain, multi-determinant Heitler-London correlations stabilize between $\simeq$8.5% and...
Abstract It is widely recognized that the effect of doping into a Mott insulator complicated and unpredictable, as can be seen by examining Hall coefficient in high T c cuprates. The effect, including electron–hole asymmetry, may more straightforward doped organic insulators owing to their simple electronic structures. Here we investigate asymmetry an carrying out electric-double-layer transistor measurements using cluster perturbation theory. calculations predict strongly anisotropic...
We propose an extended version of the symmetry-adapted variational-quantum-eigensolver (VQE) and apply it to a two-component Fermi-Hubbard model on bipartite lattice. In VQE method, Rayleigh quotient for Hamiltonian parametrized quantum state in properly chosen subspace is minimized within optimized among variational parameters implemented circuit obtain variationally ground ground-state energy. The corresponding energy derivative with respect parameter expressed as Hellmann-Feynman-type...
We present an exact diagonalization study of the self-energy two-dimensional Hubbard model. To increase range available cluster sizes we use a corrected $t$-$J$ model to compute approximate Green's functions for This allows obtain spectra clusters with 18 and 20 sites. The has several ``bands'' poles strong dispersion extended incoherent continua $k$-dependent intensity. fit by minimal this extrapolate results infinite lattice. resulting Fermi surface shows transition from hole pockets in...
Based solely on the analytical properties of single-particle Green's function fermions at finite temperatures, we show that generalized Luttinger theorem inherently possesses topological aspects. The interpretation can be introduced because i) volume is represented as winding number and thus ii) deviation theorem, expressed with a ratio between interacting noninteracting functions, also this ratio. formulation based naturally leads to two types theorem. Exploring examples single-band...
We investigate a semimetal-superconductor phase transition of two-dimensional Dirac electrons at zero temperature by large-scale and essentially unbiased quantum Monte Carlo simulations for the half-filled attractive Hubbard model on triangular lattice, in presence alternating magnetic $\pi$-flux, that is introduced to construct two points one-particle bands Fermi level. This expected describe criticality chiral XY class framework Gross-Neveu model, where, ordered phase, $U(1)$ symmetry...
We numerically investigate the quantum criticality of chiral Heisenberg universality class with total number fermion components $N$=8 in terms Gross-Neveu theory. Auxiliary-field Monte Carlo simulations are performed for square lattice Hubbard model presence a $d$-wave pairing field, inducing Dirac cones single particle spectrum. This property makes particularly interesting because it turns out to belong same on honeycomb lattice, that is canonical graphene, despite unit cells being...
We propose a quantum-classical hybrid algorithm of the power method, here dubbed as quantum to evaluate H^n|ψ⟩ with computers, where n is non-negative integer, H^ time-independent Hamiltonian interest, and |ψ⟩ state. show that number gates required for approximating H^n scales linearly in qubits, making it promising application near-term computers. Using numerical simulation, we method can control systematic errors large 100. As an application, combine our multireference...
Despite being relevant to better understand the properties of honeycomblike systems, as graphene-based compounds, electron-phonon interaction is commonly disregarded in theoretical approaches. That is, effects phonon fields on interacting Dirac electrons an open issue, particular when investigating long-range ordering. Thus, here we perform unbiased quantum Monte Carlo simulations examine Hubbard-Holstein model (HHM) half-filled honeycomb lattice. By performing careful finite-size scaling...
Counterdiabatic (CD) protocols enable fast driving of quantum states by invoking an auxiliary adiabatic gauge potential (AGP) that suppresses transitions to excited throughout the process. Usually, full spectrum original unassisted Hamiltonian is a prerequisite for constructing exact AGP, which implies CD are extremely difficult many-body systems. Here, we apply variational protocol recently proposed P. W. Claeys et al. [Phys. Rev. Lett. 123, 090602 (2019)] two-component fermionic Hubbard...
Here, the Holstein-Hubbard model at one electron per site filling -- a realistic of superconductivity that includes correlation and electron-phonon coupling is solved exactly in relevant region its phase diagram, by numerical simulations based on quantum Monte Carlo. Previous attempts were limited exponential complexity number electrons.
We formulate a finite-temperature scheme of the variational cluster approximation (VCA) particularly suitable for an exact-diagonalization solver. Based on analytical properties single-particle Green's function matrices, we explicitly show branch-cut structure logarithm complex determinant functions appearing in self-energy-functional theory (SFT) and whereby construct efficient VCA. also derive explicit formulas entropy specific heat within framework SFT. first apply method to explore...
Simultaneous control of bandfilling and bandwidth reveals the two-dimensional ground-state phase diagram a Mott transistor.
Simulating nonequilibirum dynamics of a quantum many-body system is one the promising applications computing. We simulate time evolution one-dimensional <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:msub><a:mi mathvariant="bold">Z</a:mi><a:mn>2</a:mn></a:msub></a:math> lattice gauge theory on IBM’s superconducting 156-qubit device, ibm_fez. consider Floquet circuit made Trotter decomposition Hamiltonian and focus its toward thermalization. Quantum simulation with...
Effects of W and Co on creep deformation microstructure fully annealed precipitation strengthened 15Cr-3W ferritic steels at 923 973 K have been investigated, the strengthening effects in a long-term high temperature service condition discussed. The effect addition rupture strength is higher than that further shortterm. However, life steel with 6 mass% longer 3 low stress 50 MPa K. increase content promotes formation intermetallic compounds such as χ phase. fine M23C6 carbide within grains....