Manipulating Goldstone modes via the superradiant light in a bosonic lattice gas inside a cavity

TL;DR

This paper investigates how cavity-mediated interactions in a bosonic lattice gas can manipulate Goldstone modes, revealing a novel effect of superradiant light on low-energy excitations and mode switching.

Contribution

It introduces an effective field theory for strongly-coupled bosonic gases in cavities, showing how quantum fluctuations induce switching between Goldstone modes.

Findings

Superradiant cavity light induces density imbalance effects.

Quantum fluctuations dramatically alter low-energy excitations.

Switching between type I and type II Goldstone modes observed.

Abstract

We study the low-energy excitations of a bosonic lattice gas with cavity-mediated interactions. By performing two successive Hubbard-Stratonovich transformations, we derive an effective field theory to study the strongly-coupling regime. Taking into account the quantum fluctuation, we report the unusual effect of the superradiant cavity light induced density imbalance, which has been shown to have a negligible effect on the single particle excitation in the previous studies. Instead, we show that such negligible fluctuation of density imbalance dramatically changes the behavior of the low-energy excitation and results in a free switching between two types of Goldstone modes in its single particle excitation, i.e., type I and type II with odd and even power energy-momentum dispersion, respectively. Our proposal would open a new horizon for manipulating Goldstone modes from bridging the cavity light and strongly interacting quantum matters.