Photon condensation, Van Vleck paramagnetism, and chiral cavities

TL;DR

This paper presents a gauge-invariant model of molecules in a chiral cavity with a magnetic field, demonstrating an equilibrium quantum phase transition to a photon condensate in the Van Vleck paramagnetic regime.

Contribution

It introduces a novel gauge-invariant model for molecules in a chiral cavity with a magnetic field, revealing a quantum phase transition to photon condensation.

Findings

Quantum phase transition to photon condensate occurs in Van Vleck paramagnetic molecules.

Model incorporates spatially-varying cavity electromagnetic vector potential A(r).

Chiral cavity with a uniform magnetic field B is used to demonstrate the phenomenon.

Abstract

We introduce a gauge-invariant model of planar, square molecules coupled to a quantized spatially-varying cavity electromagnetic vector potential A(r). Specifically, we choose a temporally chiral cavity hosting a uniform magnetic field B, as this is the simplest instance in which a transverse spatially-varying A(r) is at play. We show that when the molecules are in the Van Vleck paramagnetic regime, an equilibrium quantum phase transition to a photon condensate state occurs.