Dresden 2020 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 80: Quantum transport and quantum Hall effects
HL 80.1: Talk
Friday, March 20, 2020, 09:30–09:45, POT 51
Resolution of the "exponent puzzle" for the Anderson transition in doped semiconductors — Edoardo Carnio1, •Rudolf Römer2,3, and Nicholas Hine2 — 1Albert-Ludwigs-Universität Freiburg, 79104 Freiburg, Germany — 2University of Warwick, Coventry, UK — 3Université de Cergy-Pontoise, Institut d’Études Avancées, and LPTM (UMR8089 of CNRS), F-95302 Cergy-Pontoise, France
The Anderson metal-insulator transition (MIT) is central to our understanding of the quantum mechanical nature of disordered materials. Despite extensive efforts by theory and experiment, there is still no agreement on the value of the critical exponent ν describing the universality of the transition*the so-called *exponent puzzle.* In this Rapid Communication, going beyond the standard Anderson model, we employ ab initio methods to study the MIT in a realistic model of a doped semiconductor. We use linear-scaling density functional theory to simulate prototypes of sulfur-doped silicon (Si:S). From these we build larger tight-binding models close to the critical concentration of the MIT. When the dopant concentration is increased, an impurity band forms and eventually delocalizes. We characterize the MIT via multifractal finite-size scaling, obtaining the phase diagram and estimates of ν. Our results suggest an explanation of the long-standing exponent puzzle, which we link to the hybridization of conduction and impurity bands.