Quantum phase transition and excitations of the Tavis-Cummings lattice model

TL;DR

This paper investigates the quantum phase transition and elementary excitations in the Tavis-Cummings lattice model, revealing how the number of atomiclike structures per cavity influences the phase boundary and polariton excitations using the variational cluster approach.

Contribution

It introduces a detailed analysis of the phase boundary and excitations in the Tavis-Cummings lattice model, emphasizing the role of multiple atomiclike structures per cavity.

Findings

The phase boundary between Mott and superfluid phases depends on the number of atomiclike structures.

Elementary excitations are characterized as polaritons, superpositions of photons and atomic excitations.

Spectral functions and densities of states reveal the nature of light-matter quasiparticles.

Abstract

The enormous progress in controlling quantum optical and atomic systems has prompted ideas for new experimental realizations of strongly correlated many-body systems operating with light. These systems consist of photons confined in optical cavities, which interact strongly with atoms or atomiclike structures. Due to the interaction between the two particle species optical nonlinearities appear, leading to a quantum phase transition from Mott to superfluid phase. Here, we address the Tavis-Cummings lattice model, which describes light-matter systems containing multiple atomiclike structures in each cavity. In particular, we investigate the phase boundary delimiting Mott from superfluid phase and the elementary excitations of the two-dimensional Tavis-Cummings lattice model in dependence of the number of atomiclike structures per cavity. In order to obtain the results we employ the variational cluster approach. We evaluate spectral functions and densities of states of both particle species, which allows us to characterize the fundamental excitations of light-matter systems. These excitations are termed polaritons and are superpositions of photons and atomic excitations. We introduce polariton quasiparticles as appropriate linear combinations of both particle species and analyze the weights of their constituents. Our results demonstrate the dependence of the quantum phase transition and the elementary excitations on the number of atomiclike structures per cavity and provide thus valuable insight into the physics of light-matter systems.