Quantum Hall plateau transitions in disordered superconductors

TL;DR

This paper investigates a unique delocalization transition in disordered two-dimensional superconductors, revealing a direct transition between insulating phases with different quantized Hall conductances and the effects of symmetry-breaking fields.

Contribution

It identifies a new symmetry class for quasiparticles in disordered superconductors and characterizes the nature of the quantum Hall plateau transition within this class.

Findings

A direct transition between zero and two quantized Hall conductance phases.

Energy acts as a relevant symmetry-breaking field at the critical point.

The transition splits into two conventional plateau transitions under symmetry-breaking.

Abstract

We study a delocalization transition for non-interacting quasiparticles moving in two dimensions, which belongs to a new symmetry class. This symmetry class can be realised in a dirty, gapless superconductor in which time reversal symmetry for orbital motion is broken, but spin rotation symmetry is intact. We find a direct transition between two insulating phases with quantized Hall conductances of zero and two for the conserved quasiparticles. The energy of quasiparticles acts as a relevant, symmetry-breaking field at the critical point, which splits the direct transition into two conventional plateau transitions.