paper

Effective mass and tricritical point for lattice fermions localized by a random mass

arXiv:1004.1111 · doi:10.1103/PhysRevB.81.214203

Abstract

This is a numerical study of quasiparticle localization in symmetry class \textit{BD} (realized, for example, in chiral \textit{p}-wave superconductors), by means of a staggered-fermion lattice model for two-dimensional Dirac fermions with a random mass. For sufficiently weak disorder, the system size dependence of the average (thermal) conductivity is well described by an effective mass , dependent on the first two moments of the random mass . The effective mass vanishes linearly when the average mass , reproducing the known insulator-insulator phase boundary with a scale invariant dimensionless conductivity and critical exponent . For strong disorder a transition to a metallic phase appears, with larger but the same . The intersection of the metal-insulator and insulator-insulator phase boundaries is identified as a \textit{repulsive} tricritical point.

6 pages, 9 figures

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