The Experts below are selected from a list of 315 Experts worldwide ranked by ideXlab platform

Sylwester Porowski - One of the best experts on this subject based on the ideXlab platform.

  • Properties of Metal-Insulator Transition and electron spin relaxation in GaN:Si
    Physical Review B, 2011
    Co-Authors: Agnieszka Wolos, Zbysław Wilamowski, M. Piersa, W. Strupinski, Boleslaw Lucznik, Izabella Grzegory, Sylwester Porowski
    Abstract:

    We investigate properties of doping-induced Metal-Insulator Transition in GaN:Si by means of electron spin resonance and Hall effect. While increasing the doping concentration, Si-related bands are formed below the bottom of the GaN conduction band. The D0 band of single-occupied Si donor sites is centered 27 meV below the bottom of the GaN conduction band, the D- band of double-occupied Si states at 2.7 meV below the bottom of the GaN conduction band. Strong damping of the magnetic moment occurs due to filling of the D- states at Si concentrations approaching the Metal-Insulator Transition. Simultaneously, shortening of electron spin relaxation time due to limited electron lifetime in the single-occupied D0 band is observed. The Metal-Insulator Transition occurs at the critical concentration of uncompensated donors equal to about 1.6 * 10^18 cm^-3. Electronic states in Metallic samples beyond the Metal-Insulator Transition demonstrate non-magnetic character of double-occupied states.

  • Metal‐Insulator Transition in GaN Crystals
    physica status solidi (b), 1996
    Co-Authors: Piotr Perlin, Izabella Grzegory, Wojciech Knap, Jean Camassel, Alain Polian, Jean-claude Chervin, Tadeusz Suski, Sylwester Porowski
    Abstract:

    By means of high-pressure Raman spectroscopy of coupled LO phonon-plasmon modes, a qualitatively new model of the Metal-Insulator Transition observed in bulk GaN crystals at pressure around 20 GPa is proposed. This Transition was interpreted recently as caused by the emergence of the localized donor state into the energy gap of GaN. Our new experimental evidence suggests that two types of donors can supply electrons to the bulk crystal: the first of a localized character and the second of a shallow character with contributions to the electron concentration of 5 × 1019 and 3 × 1018 cm−3, respectively. The localized state can be associated with the nitrogen vacancy, while the shallow state can be tentatively attributed to impurities such as oxygen. A number of interesting phenomena take place beyond the Metal-Insulator Transition in bulk GaN and an attempt to explain them will be made in the present work.

R. Mark Wilson - One of the best experts on this subject based on the ideXlab platform.

Jaichan Lee - One of the best experts on this subject based on the ideXlab platform.

  • Metal-Insulator Transition in low dimensional La0.75Sr0.25VO3 thin films
    Applied Physics Letters, 2011
    Co-Authors: Tran M. Dao, Partha S. Mondal, Y. Takamura, E. Arenholz, Jaichan Lee
    Abstract:

    We report on the Metal-Insulator Transition that occurs as a function of film thickness in ultrathin La0.75Sr0.25VO3 films. The Metal-Insulator Transition displays a critical thickness of 5 unit cell. Above the critical thickness, Metallic films exhibit a temperature driven Metal-Insulator Transition with weak localization behavior. With decreasing film thickness, oxygen octahedron rotation in the films increases, causing enhanced electron-electron correlation. The electron-electron correlations in ultrathin films induce the Transition from Metal to Insulator in addition to Anderson localization.

Gillian A. Gehring - One of the best experts on this subject based on the ideXlab platform.

Sandro Sorella - One of the best experts on this subject based on the ideXlab platform.

  • universal quantum criticality in the Metal Insulator Transition of two dimensional interacting dirac electrons
    Physical Review X, 2016
    Co-Authors: Yuichi Otsuka, Seiji Yunoki, Sandro Sorella
    Abstract:

    The Metal-Insulator Transition is an important aspect of quantum mechanics. Using lattice models populated with Dirac electrons, researchers present a numerically exact investigation of this Transition.

  • universal quantum criticality in the Metal Insulator Transition of two dimensional interacting dirac electrons
    arXiv: Strongly Correlated Electrons, 2015
    Co-Authors: Yuichi Otsuka, Seiji Yunoki, Sandro Sorella
    Abstract:

    The Metal-Insulator Transition has been a subject of intense research since Nevil Mott has first proposed that the Metallic behavior of interacting electrons could turn to the insulating one as electron correlations increase. Here, we consider electrons with massless Dirac-like dispersion in two spatial dimensions, described by the Hubbard models on two geometrically different lattices, and perform numerically exact calculations on unprecedentedly large systems that, combined with a careful finite size scaling analysis, allow us to explore the quantum critical behavior in the vicinity of the interaction-driven Metal-Insulator Transition. We find thereby that the Transition is continuous and determine the quantum criticality for the corresponding universality class, which is described in the continuous limit by the Gross-Neveu model, a model extensively studied in quantum field theory. We furthermore discuss a fluctuation-driven scenario for the Metal-Insulator Transition in the interacting Dirac electrons: the Metal-Insulator Transition is triggered only by the vanishing of the quasiparticle weight but not the Dirac Fermi velocity, which instead remains finite near the Transition. This important feature cannot be captured by a simple mean-field or Gutzwiller-type approximate picture, but is rather consistent with the low energy behavior of the Gross-Neveu model.