Temperature enhancement of thermal Hall conductance quantization

TL;DR

This paper investigates how disorder-induced thermal metal phases can mimic non-Abelian signatures in thermal Hall conductance, revealing that quantization can improve with temperature and complicate experimental identification.

Contribution

It demonstrates that a non-topological thermal metal phase can produce quantized thermal Hall conductance, challenging the interpretation of such signals as evidence of non-Abelian quasiparticles.

Findings

Disorder-induced thermal metal phases can mimic quantized thermal Hall signals.

Quantization of thermal Hall conductance can improve with increasing temperature.

Numerical evidence supports the possibility of non-topological phases exhibiting quantized responses.

Abstract

The quest for non-Abelian quasiparticles has inspired decades of experimental and theoretical efforts, where the scarcity of direct probes poses a key challenge. Among their clearest signatures is a thermal Hall conductance with quantized half-integer value in natural units $ \pi^2 k_B^2 T /3 h$ ($T$ is temperature, $h$ the Planck constant, $k_B$ the Boltzmann constant). Such a value was indeed recently observed in a quantum-Hall system and a magnetic insulator. We show that a non-topological "thermal metal" phase that forms due to quenched disorder may disguise as a non-Abelian phase by well approximating the trademark quantized thermal Hall response. Remarkably, the quantization here improves with temperature, in contrast to fully gapped systems. We provide numerical evidence for this effect and discuss its possible implications for the aforementioned experiments.