A5113599345- Surface and Thin Film Phenomena
- Advanced Chemical Physics Studies
- X-ray Diffraction in Crystallography
- Crystallization and Solubility Studies
- Electron and X-Ray Spectroscopy Techniques
- Quantum and electron transport phenomena
- nanoparticles nucleation surface interactions
- Physics of Superconductivity and Magnetism
- Advanced Condensed Matter Physics
- Semiconductor materials and interfaces
- Magnetic properties of thin films
- Theoretical and Computational Physics
- Semiconductor Quantum Structures and Devices
- Molecular Junctions and Nanostructures
- Chemical and Physical Properties of Materials
- Silicon and Solar Cell Technologies
- Magnetic and transport properties of perovskites and related materials
- Force Microscopy Techniques and Applications
- Graphene research and applications
- Advanced Materials Characterization Techniques
- Semiconductor materials and devices
- Surface Chemistry and Catalysis
- Fusion materials and technologies
- Iron-based superconductors research
- Boron and Carbon Nanomaterials Research
The University of Tokyo
2009-2024
Tokyo University of Science
1999-2021
Hitachi (Japan)
2016
Keio University
2016
Tottori University
2010-2015
Institute for Solid State Physics and Optics
2007
SPring-8
2005
Kavli Institute for the Physics and Mathematics of the Universe
2005
Tokyo University of Agriculture
1960
Motivated by the recent experimental discovery of superconductivity in infinite-layer nickelate Nd0.8Sr0.2NiO2 [Li et al., Nature 572, 624 (2019)], we study how correlated Ni 3dx2-y2 electrons NiO2 layer interact with Nd layer. We show that three orbitals are necessary to represent electronic structure around Fermi level: 3dx2-y2, 5d3z2-r2, and a bonding orbital made from an interstitial s 5dxy orbital. By constructing three-orbital model for these states, find hybridization between state...
We derive effective Hubbard-type Hamiltonians of $\kappa$-(ET)$_2X$, using an {\em ab initio} downfolding technique, for the first time organic conductors. They contain dispersions highest occupied Wannier-type molecular orbitals with nearest neighbor transfer $t$$\sim$0.067 eV a metal $X$=Cu(NCS)$_2$ and 0.055 Mott insulator $X$=Cu$_2$(CN)$_3$, as well screened Coulomb interactions. It shows unexpected differences from conventional extended H\"uckel results, especially much stronger onsite...
RESPACK is a first-principles calculation software for evaluating the interaction parameters of materials and able to calculate maximally localized Wannier functions, response functions based on random phase approximation related optical properties, frequency-dependent electronic parameters. receives its input data from band-calculation code using norm-conserving pseudopotentials with plane-wave basis sets. Automatic generation scripts that convert band-structure results inputs are prepared...
For the purposes of long-term use tungsten divertor walls, formation process fuzzy nanostructure induced by exposure to helium plasma was studied. In present paper, nanostructure's has been successfully reproduced new hybrid simulation method in which deformation material due pressure bubbles simulated molecular dynamics and diffusion atoms random walk based on Monte Carlo method. By results, surface height increased only when retention under steady state. It proven that growth brought about...
We present ab initio two-dimensional extended Hubbard-type multiband models for EtMe${}_{3}$Sb[Pd(dmit)${}_{2}$]${}_{2}$ (where dmit is 1,3-dithiole-2-thione-4,5-dithiolate) and $\ensuremath{\kappa}$-(BEDT-TTF)${}_{2}$Cu(NCS)${}_{2}$ [where BEDT-TTF bis(ethylenedithio)-tetrathiafulvalene] after a downfolding scheme based on the constrained random-phase approximation (cRPA) maximally localized Wannier orbitals, together with dimensional downfolding. In Pd(dmit)${}_{2}$ salt, antibonding state...
The bursting and expansion of helium bubbles near the surface a tungsten material were investigated by using molecular dynamics (MD) simulation. These bubble processes are considered to be important in formation mechanism fuzzy nano-structures. phase diagram occurrence was obtained our MD results simulation indicate that with radius 1.0 nm needs high pressure several tens GPa burst expand structures under scale ten nanometers. Moreover, from viewpoint dynamics, imply concavities convexities...
We present an ab initio method for calculating effective onsite Coulomb interactions of solid. The is based on constrained local density functional theory formulated in terms maximally localized Wannier functions. This scheme can be implemented with any basis, and thus allows us to perform the calculation plane-wave-based electronic-structure codes. apply developed evaluation interaction 3$d$ transition-metal series. results are discussed using a heuristic formula screened interactions.
We carried out a comprehensive study on the B1s core-level X-ray photoelectron spectroscopy (XPS) binding energies for B clusters in crystalline Si using first-principles calculation with careful evaluation of local potential boundary condition model system, where convergence within 0.1 eV was confirmed supercell size. For ion-implanted samples, we identified experimental peaks due to and threefold as icosahedral B12 〈001〉B-Si defects, respectively. as-doped samples prepared by plasma...
The problem of the relative energetic stabilities high-order reconstructions Ge(001) surface is revisited with more refined first-principles calculations. Deducing parameters Ising model from this result, we perform Monte Carlo simulations phase transition asymmetric dimer directions. simulation reproduces fairly well experimental temperature an x-ray-diffraction experiment. potential-energy curve flip-flop motion in $p(2\ifmmode\times\else\texttimes\fi{}1)$ structure determined. obtained...
We have studied the electronic structure change of Cu(100) surface due to lattice strain both experimentally and theoretically. In experiments, is compressed by partial nitrogen adsorption. Detailed measurements were made using angle-resolved photoemission spectroscopy with synchrotron $\mathrm{He}\phantom{\rule{0.2em}{0ex}}I$ radiations. mainly focused on states at $d$-band top bottom, also $sp$ (Shockley state) $\overline{\mathrm{X}}$. The bottom shifts toward higher binding energy, while...
We report the discovery of nonlinear conductivity along c-axis in a single crystal Ca5Ir3O12, which indicates semiconducting behavior with narrow band gap ∼0.2 eV. The resistivity decreases increase applied current. This nonlinearity is reversible direction also show ab initio density functional structures and Fermi surface. found that spin–orbit interactions result an appreciable change low-energy electronic structure; interaction splits metallic bands leads to pocket-like structure, thus...
We present an ab initio derivation method for effective low-energy Hamiltonians of material with strong spin-orbit interactions. The Hamiltonian is described in terms the Wannier function spinor form, and interactions are derived constrained random phase approximation (cRPA) method. Based on this formalism developed code, we derive a interaction ${\mathrm{Ca}}_{5}{\mathrm{Ir}}_{3}{\mathrm{O}}_{12}$. This system consists three edge-shared ${\mathrm{IrO}}_{6}$ octahedral chains arranged along...
An ab initio downfolding method is formulated to construct low-dimensional models for correlated electrons. In addition the band by constrained random phase approximation 3D models, screening away from target layer (chain) further involved. Eliminating off-target degrees of freedom, namely, dimensional yields models. The applied derive a 2D model layered superconductor LaFeAsO, where interlayer crucially makes effective interaction short ranged and reduces onsite Coulomb interactions 10-20...
The reconstruction on a Ge(001) surface is locally and reversibly changed between c (4×2) p (2×2) by controlling the bias voltage of scanning tunneling microscope (STM) at 80 K. It with sample V b ≤-0.7 V. This structure can be maintained ≤0.6 When higher than 0.8 during scanning, changes to (2×2). then ≥-0.6 observed local change hysteresis attributed energy transfer process from electron Ge lattice in electric field under STM tip.
A topological defect, which is formed at the boundary between two stable superstructures on clean Ge(001) surface, $c(4\ifmmode\times\else\texttimes\fi{}2)$ and $p(2\ifmmode\times\else\texttimes\fi{}2)$, can be laterally manipulated $80\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ by injection of carriers into surface states from a metal tip scanning tunneling microscope (STM). We measured probability defect motion as functions direction to point, distance them, bias voltage during carrier...
We carried out a comprehensive study on the B 1s core-level X-ray photoelectron spectroscopy (XPS) binding energies and formation for boron defects in crystalline silicon by first-principles calculation with careful evaluation of local potential boundary condition model system using supercell corresponding to 1000 Si atoms. It is reconfirmed that cubo-octahedral B12 cluster crystal unstable exists at saddle point decaying icosahedral S4 clusters. The electrically active clusters without any...
We have observed a novel modification of surface state due to local strain field induced by nanopattern formation. N adsorption on the Cu(100) induces nanoscale grid pattern, where clean Cu regions remain periodically. The lattice is contracted region adjacent c(2 x 2)N domains, which larger constant. On this patterned surface, we investigated Tamm-type at M means angle-resolved ultraviolet photoelectron spectroscopy. binding energy Tamm shifts toward Fermi level continuously with increasing...
Ultraviolet photoelectron spectra (UPS) of metallofullerene, ${\mathrm{La}}_{2}@{\mathrm{C}}_{78}$ were measured using a synchrotron-radiation light source. Its spectral onset energy was $0.70\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ below the Fermi level, indicating semiconductive nature this metallofullerene. The UPS consisted numerous crests and troughs. Further, change in intensity upon tuning excitation observed; however, not as large those observed for other fullerenes. differ...
The initial stage of molecular oxygen adsorption on Cu(001) surface is investigated by scanning tunneling microscopy and first principles calculations. molecule always dissociates the between 5 300 K. dissociated atoms adsorb at two 4-fold hollow sites separated twice nearest-neighbor distance Cu in close-packed directions, [110] [1̅10]. This most stable structure evaluated for pair adsorbed site calculation. stay same below 80 K, thermally migrate above