Exceptional Spin Liquids from Couplings to the Environment

TL;DR

This paper introduces a new class of spin liquids arising from environmental coupling in the Kitaev honeycomb model, featuring exceptional points, Fermi arcs, and stability against perturbations, with potential experimental implications.

Contribution

It demonstrates the emergence of exceptional points and a novel spin liquid phase in an open Kitaev system coupled to an environment, expanding the understanding of spin liquids beyond closed systems.

Findings

Emergence of exceptional points with Fermi arcs in the coupled system

Stability of the new phase against all perturbations

Significant boundary sensitivity due to non-Hermitian skin effect

Abstract

We establish the appearance of a qualitatively new type of spin liquid with emergent exceptional points when coupling to the environment. We consider an open system of the Kitaev honeycomb model generically coupled to an external environment. In extended parameter regimes, the Dirac points of the emergent Majorana fermions from the original model are split into exceptional points with Fermi arcs connecting them. In glaring contrast to the original gapless phase of the honeycomb model which requires time-reversal symmetry, this new phase is stable against all perturbations. The system also displays a large sensitivity to boundary conditions resulting from the non-Hermitian skin effect with telltale experimental consequences. Our results point to the emergence of new classes of spin liquids in open systems which might be generically realized due to unavoidable couplings with the environment.