Quarter-quantized thermal Hall effect with parity anomaly

TL;DR

This paper demonstrates that in certain superconducting systems, a quarter-quantized thermal Hall effect arises due to Majorana surface states and parity anomaly, with potential experimental realizations in magnetic topological insulators.

Contribution

It introduces a novel quarter-quantized thermal Hall effect linked to Majorana surface states and parity anomaly, supported by a conductor-network model analysis.

Findings

Quarter-quantized thermal Hall conductance observed.

Presence of a single gapless Majorana cone confirmed.

Stability of quantization under temperature variations.

Abstract

We show that in the proximity of s-wave superconductors, the magnetic topological surface states can transform into Majorana surface state, featuring a single gapless Majorana cone with parity anomaly when the superconducting pairing gap matches the surface magnetization gap. The emergence of $N=1/2$ Majorana chiral edge current is observed at the boundaries between the gap region and the gapless region. Additionally, in systems with a single gapless Majorana cone, a quarter-quantized thermal Hall conductance appears under the dephasing. By mapping the system to a conductor-network model, we identify the appearance of 1/4 chiral heat channels as the cause of the quarter-quantized Hall thermal conductance. We observe the stability of this quarter-quantized thermal conductance under temperature variations, serving as a distinctive feature indicating the presence of a single gapless Majorana cone in the system. Our models can be experimentally realized using magnetic topological insulators or iron-based superconductors.