Dicke materials as a potential resource for quantum squeezing

We introduce the term Dicke materials for certain magnetic materials whose low energy physics can be effectively described by a Dicke model. We show how a Dicke model can be derived from spin exchange interactions in magnetic materials containing two species of magnetic atoms. Analogous to the paradigmatic Dicke model describing light-matter interactions, these materials also exhibit signatures of a superradiant phase transition. The ground state near the superradiant phase transition is expected to be squeezed, making Dicke materials a potential resource for quantum metrology and witnessing entanglement. However, as an entanglement measure, squeezing can be sensitive to perturbations that are otherwise irrelevant for usual correlation functions and order parameters. Motivated by the prospect of observing squeezing in such Dicke materials, we study the robustness of ground state squeezing under ubiquitous imperfections such as finite temperature, disorder and local interactions. Using a mix of analytical and numerical techniques, we show that the squeezing obtained is perturbatively stable against these imperfections and quantitatively evaluate regimes promising for experimental observation.