Bose-glass phases of ultracold atoms due to cavity backaction

TL;DR

This paper explores how cavity backaction induces Bose-glass phases in ultracold bosonic atoms, revealing a new mechanism where quantum fluctuations mimic disorder effects in a controlled quantum system.

Contribution

It introduces a novel cavity QED setup where quantum fluctuations lead to Bose-glass phases, a phenomenon typically associated with disorder, using a Bose-Hubbard model with cavity-dependent coefficients.

Findings

Cavity backaction induces checkerboard density clusters in ultracold atoms.

The ground state exhibits Bose-glass characteristics: no superfluidity, finite compressibility.

Quantum fluctuations can mimic disorder effects in a controlled quantum environment.

Abstract

We determine the quantum ground-state properties of ultracold bosonic atoms interacting with the mode of a high-finesse resonator. The atoms are confined by an external optical lattice, whose period is incommensurate with the cavity mode wave length, and are driven by a transverse laser, which is resonant with the cavity mode. While for pointlike atoms photon scattering into the cavity is suppressed, for sufficiently strong lasers quantum fluctuations can support the build-up of an intracavity field, which in turn amplifies quantum fluctuations. The dynamics is described by a Bose-Hubbard model where the coefficients due to the cavity field depend on the atomic density at all lattice sites. Quantum Monte Carlo simulations and mean-field calculations show that for large parameter regions cavity backaction forces the atoms into clusters with a checkerboard density distribution. Here, the ground state lacks superfluidity and possesses finite compressibility, typical of a Bose-glass. This system constitutes a novel setting where quantum fluctuations give rise to effects usually associated with disorder.