A cavity-induced artificial gauge field in a Bose-Hubbard ladder

TL;DR

This paper theoretically explores how ultracold bosonic atoms in a ladder structure coupled to an optical cavity can exhibit artificial gauge fields, leading to various self-organized quantum phases including superfluid, Mott insulator, and vortex states.

Contribution

It introduces a cavity-induced gauge field in a Bose-Hubbard ladder and characterizes the resulting complex phase diagram using advanced numerical methods.

Findings

Observation of superfluid to Mott insulator transitions

Identification of Meissner, vortex liquid, and vortex lattice phases

Stabilization of a biased-ladder phase breaking leg symmetry

Abstract

We consider theoretically ultracold interacting bosonic atoms confined to quasi-one-dimensional ladder structures formed by optical lattices and coupled to the field of an optical cavity. The atoms can collect a spatial phase imprint during a cavity-assisted tunneling along a rung via Raman transitions employing a cavity mode and a transverse running wave pump beam. By adiabatic elimination of the cavity field we obtain an effective Hamiltonian for the bosonic atoms, with a self-consistency condition. Using the numerical density matrix renormalization group method, we obtain a rich steady state diagram of self-organized steady states. Transitions between superfluid to Mott-insulating states occur, on top of which we can have Meissner, vortex liquid, and vortex lattice phases. Also a state that explicitly breaks the symmetry between the two legs of the ladder, namely the biased-ladder phase is dynamically stabilized.