Quantum phase transition of ultracold bosons in the presence of a non-Abelian synthetic gauge field

TL;DR

This paper investigates how non-Abelian synthetic gauge fields influence the phase transition and properties of ultracold bosons in optical lattices, revealing non-monotonic phase boundaries and momentum distribution changes.

Contribution

It provides a detailed analysis of the superfluid-insulator transition under non-Abelian gauge fields, including excitation spectra and spatial superfluid patterns, which is novel.

Findings

Superfluid-insulator phase boundary shows non-monotonic dependence on gauge field strength.

Bosons develop peaks at non-zero momenta near the transition.

Spatial patterns of superfluid density are induced by the non-Abelian gauge potential.

Abstract

We study the Mott phases and the superfluid-insulator transition of two-component ultracold bosons on a square optical lattice in the presence of a non-Abelian synthetic gauge field, which renders a SU(2) hopping matrix for the bosons. Using a resummed hopping expansion, we calculate the excitation spectra in the Mott insulating phases and demonstrate that the superfluid-insulator phase boundary displays a non-monotonic dependence on the gauge field strength. We also compute the momentum distribution of the bosons in the presence of the non-Abelian field and show that they develop peaks at non-zero momenta as the superfluid-insulator transition point is approached from the Mott side. Finally, we study the superfluid phases near the transition and discuss the induced spatial pattern of the superfluid density due to the presence of the non-Abelian gauge potential.