Quantized electrical, thermal, and spin transports of non-Hermitian clean and dirty two-dimensional topological insulators and superconductors

TL;DR

This paper investigates quantized electrical, thermal, and spin transport properties in non-Hermitian two-dimensional topological insulators and superconductors, revealing regimes of quantization and the effects of disorder and non-Hermiticity.

Contribution

It provides the first comprehensive calculation of topological transport in non-Hermitian models across all five Altland-Zirnbauer classes, including effects of disorder and experimental setups.

Findings

Quantized Hall and spin conductivities in non-Hermitian topological phases.

Half-quantized thermal conductivities in certain non-Hermitian pairings.

Disappearance of topological responses under strong disorder and increasing non-Hermiticity.

Abstract

From lattice-regularized models, devoid of any non-Hermitian (NH) skin effects, here we compute the electrical ($\sigma_{xy}$), thermal ($\kappa_{xy}$), and spin ($\sigma^{sp}_{xy}$) Hall, and the electrical ($G_{xx}$) and thermal ($G^{th}_{xx}$) longitudinal conductivities for appropriate NH planar topological insulators and superconductors related to all five non-trivial Altland-Zirbauer symmetry classes in their Hermitian limits. These models feature real eigenvalues over an extended NH parameter regime, only where the associated topological invariants remain quantized. In this regime, the NH quantum anomalous and spin Hall insulators show quantized $\sigma_{xy}$ and $G_{xx}$, respectively, the NH $p+ip$ ($p \pm ip$) pairing shows half-quantized $\kappa_{xy}$ ($G^{th}_{xx}$), while the NH $d+id$ pairing shows quantized $\kappa_{xy}$ and $\sigma^{sp}_{xy}$ in the clean and weak disorder (due to random pointlike charge impurities) regimes. We compute these quantities in experimentally realizable suitable six-terminal setups using the Kwant software package. But, in the strong disorder regime, all these topological responses vanish and with the increasing non-Hermiticity in the system this generic phenomenon occurs at weaker disorder.