Time-Reversal Phase Transition at the Edge of 3d Topological Band Insulator

TL;DR

This paper investigates the nature of the time-reversal symmetry-breaking phase transition at the edge of 3D topological insulators, revealing it as a 3D Ising transition with well-defined quasiparticles at criticality.

Contribution

It demonstrates that the T-breaking transition at the edge of 3D topological insulators is a 3D Ising transition, differing from conventional theories, with implications for quasiparticle behavior.

Findings

The T-breaking phase transition is a 3D Ising transition.

Quasiparticles remain well-defined in the quantum critical regime.

The theory differs from the Hertz-Millis model for zero-momentum order parameters.

Abstract

We study the time reversal (T) symmetry breaking of 2d helical fermi liquid, with application to the edge states of 3d topological band insulators with only one two-component Dirac fermion at finite chemical potential, as well as other systems with spin-orbit coupling. The T-breaking Ising order parameter is not over-damped and the theory is different from the ordinary Hertz-Millis theory for order parameters at zero momentum. We argue that the T-breaking phase transition is an 3d Ising transition, and the quasiparticles are well-defined in the quantum critical regime.