Metal-Insulator Transition Revisited for Cold Atoms in Non-Abelian Gauge Potentials

TL;DR

This paper explores the realization of metal-insulator transitions in ultracold atoms within two-dimensional optical lattices under non-Abelian gauge potentials, revealing unique spectral and localization features influenced by atomic momenta.

Contribution

It presents the first study of metal-insulator transitions for non-Abelian U(2) gauge fields in cold atoms, highlighting how atomic momenta affect the spectrum and localization transition.

Findings

Spectrum is fragmented by atomic momentum.

Localization transition can be tuned by atomic momentum.

Unique spectral features such as step structures and satellite fringes.

Abstract

We discuss the possibility of realizing metal-insulator transitions with ultracold atoms in two-dimensional optical lattices in the presence of artificial gauge potentials. Such transitions have been extensively studied for magnetic fields corresponding to Abelian gauges; they occur when the magnetic flux penetrating the lattice plaquette is an irrational multiple of the magnetic flux quantum. Here we present the first study of these transitions for non-Abelian U(2) gauge fields, which can be realized with atoms with two pairs of degenerate internal states. In contrast to the Abelian case, the spectrum and localization transition in the non-Abelian case is strongly influenced by atomic momenta. In addition to determining the localization boundary, the momentum fragments the spectrum and the minimum energy viewed as a function of momentum exhibits a step structure. Other key characteristics of the non-Abelian case include the absence of localization for certain states and satellite fringes around the Bragg peaks in the momentum distribution and an interesting possibility that the transition can be tuned by the atomic momenta.