Griffiths phase in the thermal quantum Hall effect

TL;DR

This paper investigates the Griffiths phase in disordered two-dimensional superconductors exhibiting the thermal quantum Hall effect, revealing a divergence in the quasiparticle density of states caused by rare disorder configurations.

Contribution

It identifies and characterizes a Griffiths phase in the thermal quantum Hall effect, highlighting the role of rare disorder configurations in the density of states divergence.

Findings

Disordered superconductors can support a Griffiths phase with divergent density of states.

The divergence follows a non-universal power law with an exponent greater than one.

Rare disorder configurations significantly influence the phase diagram and physical properties.

Abstract

Two dimensional disordered superconductors with broken spin-rotation and time-reversal invariance, e.g. with p_x+ip_y pairing, can exhibit plateaus in the thermal Hall coefficient (the thermal quantum Hall effect). Our numerical simulations show that the Hall insulating regions of the phase diagram can support a sub-phase where the quasiparticle density of states is divergent at zero energy, \rho(E)\sim |E|^{1/z-1}, with a non-universal exponent $z>1$, due to the effects of rare configurations of disorder (``Griffiths phase'').