Insulator to superfluid transition in coupled photonic cavities in two dimensions

TL;DR

This paper investigates the phase transition from insulator to superfluid in a two-dimensional lattice of coupled photonic cavities using quantum Monte Carlo simulations, revealing critical behavior consistent with a density-driven Mott-superfluid transition.

Contribution

It provides the first systematic quantum Monte Carlo study of the insulator-superfluid transition in coupled photonic cavities, highlighting the absence of multicritical points with z=1.

Findings

Critical behavior matches density-driven Mott-superfluid transition with z=2.

No multicritical points with z=1 at the tips of insulating lobes.

Demonstrates limitations of modeling polaritons as structureless bosons.

Abstract

A system of coupled photonic cavities on a two-dimensional square lattice is systematically investigated using the stochastic series expansion quantum Monte Carlo method. The ground state phase diagram contains insulating phases with integer polariton densities surrounded by a superfluid phase. The finite-size scaling of the superfluid density is used to determine the phase boundaries accurately. We find that the critical behavior is that of the generic, density-driven Mott-superfluid transition with dynamic exponent $z=2$, with no special multicritical points with $z=1$ at the tips of the insulating-phase lobes (as exist in the case of the Bose-Hubbard model). This demonstrates a limitation of the description of polaritons as structureless bosons.