Non-Hermitian minimal Kitaev chains

TL;DR

This paper shows that non-Hermitian effects, arising naturally from coupling to reservoirs, extend the stability of Majorana-like zero modes in a minimal Kitaev chain, enabling broader experimental realization.

Contribution

It demonstrates that non-Hermitian couplings stabilize and expand the parameter space of poor man's Majorana zero modes in a minimal Kitaev chain.

Findings

Non-Hermitian couplings induce exceptional points.

Zero-energy real lines are stabilized and tunable.

Topologically protected spectral degeneracies are observed.

Abstract

Starting from a double quantum dot realization of a minimal Kitaev chain, we demonstrate that non-Hermicity stabilizes the so-called poor man's Majorana zero modes in a region of parameter space that is much broader than in the Hermitian regime. In particular, we consider the simplest non-Hermitian mechanism which naturally appears due to coupling to normal reservoirs and is commonly present in all transport experiments. Specifically, such couplings induce exceptional points which connect stable and highly tunable zero energy real lines that are well separated from the quasicontinuum. Such zero-energy lines reflect spectral degeneracies protected by topology and represent the non-Hermitian generalization of the Hermitian poor mans Majorana modes occurring at single points in parameter space. Our findings pave the way for realizing robust non-Hermitian effects by combining unconventional superconductors and non-Hermitian topology.