Time-of-flight patterns of ultra-cold bosons in optical lattices in various Abelian artificial magnetic field gauges

TL;DR

This paper calculates time-of-flight patterns of strongly interacting ultra-cold bosons in optical lattices under various artificial magnetic field configurations, revealing potential experimental signatures of gauge choices and exotic quantum phases.

Contribution

It introduces a quantum rotor and Bogolyubov-based method to analyze time-of-flight patterns for different magnetic flux geometries, including uniform, staggered, and checkerboard configurations.

Findings

Time-of-flight patterns can verify gauge choices in experiments.

Identification of non-zero momentum condensates and Dirac cones.

Differences between artificial and real magnetic fields in condensed matter.

Abstract

We calculate the time-of-flight patterns of strongly interacting bosons confined in two-dimensional square lattice in the presence of an artificial magnetic field using quantum rotor model that is inherently combined with the Bogolyubov approach. We consider various geometries of the magnetic flux, which are expected to be realizable, or have already been implemented in experimental settings. The flexibility of the method let us to study cases of the artificial magnetic field being uniform, staggered or forming a checkerboard configuration. Effects of additional temporal modulation of the optical potential that results from application of Raman lasers driving particle transitions between lattice sites are also included. The presented time-of-flight patterns may serve as a verification of chosen gauge in experiments, but also provide important hints on unconventional, non-zero momentum condensates, or possibility of observing graphene-like physics resulting from occurrence of Dirac cones in artificial magnetic fields in systems of ultra-cold bosons in optical lattices. Also, we elucidate on differences between effects of magnetic field in solids and the artificial magnetic field in optical lattices, which can be controlled on much higher level leading to effects not possible in condensed matter physics.