Spin liquids in open quantum systems

We establish the appearance of a qualitatively new type of spin liquid with emergent exceptional band-touching behaviours when coupling to the environment. We consider an open system of the Kitaev model generically coupled to an external environment. In extended parameter regimes, the usual band crossings of the emergent Majorana fermions from the original model are split into exceptional band crossings. 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.