Density of quasiparticle states for a two-dimensional disordered system: Metallic, insulating, and critical behavior in the class-D thermal quantum Hall effect

A. Mildenberger, F. Evers, A. D. Mirlin, and J. T. Chalker
Phys. Rev. B 75, 245321 – Published 19 June 2007

Abstract

We investigate numerically the quasiparticle density of states ϱ(E) for a two-dimensional, disordered superconductor in which both time-reversal and spin-rotation symmetries are broken. As a generic single-particle description of this class of systems (symmetry class D), we use the Cho-Fisher version of the network model. This has three phases: a thermal insulator, a thermal metal, and a quantized thermal Hall conductor. In the thermal metal, we find a logarithmic divergence in ϱ(E) as E0, as predicted from sigma model calculations. Finite-size effects lead to superimposed oscillations, as expected from random-matrix theory. In the thermal insulator and quantized thermal Hall conductor, we find that ϱ(E) is finite at E=0. At the plateau transition between these phases, ϱ(E) decreases toward zero as E is reduced, in line with the result ϱ(E)Eln(1E) derived from calculations for Dirac fermions with random mass.

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  • Received 25 October 2006

DOI:https://doi.org/10.1103/PhysRevB.75.245321

©2007 American Physical Society

Authors & Affiliations

A. Mildenberger1,2, F. Evers2,3, A. D. Mirlin2,3,*, and J. T. Chalker3,4

  • 1Fakultät für Physik, Universität Karlsruhe, 76128 Karlsruhe, Germany
  • 2Institut für Nanotechnologie, Forschungszentrum Karlsruhe, 76021 Karlsruhe, Germany
  • 3Institut für Theorie der Kondensierten Materie, Universität Karlsruhe, 76128 Karlsruhe, Germany
  • 4Theoretical Physics, University of Oxford, 1 Keble Road, Oxford OX1 3NP, United Kingdom

  • *Also at Petersburg Nuclear Physics Institute, 188300 St. Petersburg, Russia.

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Vol. 75, Iss. 24 — 15 June 2007

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