Exactly Solvable Phase Transition in a Cavity-Coupled 1D Ising Chain

TL;DR

This paper demonstrates an exactly solvable model where a 1D Ising chain coupled to a cavity photon mode exhibits a finite-temperature superradiant phase transition, contrary to classical expectations.

Contribution

It introduces a novel exactly solvable model showing phase transitions in a 1D spin chain coupled to a cavity, highlighting photon-mediated long-range interactions.

Findings

Phase transition occurs in the coupled 1D Ising chain

Finite-temperature superradiant phase transition is demonstrated

Long-range interactions mediated by photons enable the transition

Abstract

Although one-dimensional classical spin chains do not exhibit phase transitions, we found that a phase transition does occur when they are coupled to a cavity photon mode. This provides the simplest exactly solvable examples demonstrating that finite-temperature superradiant phase transitions can emerge from long-range fully connected interactions mediated by photons and interactions within the material.