Topological phase transitions driven by non-Abelian gauge potentials in optical square lattices

TL;DR

This paper investigates how non-Abelian gauge potentials in optical square lattices induce topological phase transitions, revealing new phases and diagnostic methods for ultracold fermion systems.

Contribution

It introduces a model showing topological phase transitions driven by non-Abelian gauge fields and proposes a method to detect these phases via spin polarization measurements.

Findings

Identified a semimetal/insulator phase transition.

Discovered a topological phase transition between insulating phases.

Proposed spin polarization as a diagnostic tool.

Abstract

We analyze a tight-binding model of ultracold fermions loaded in an optical square lattice and subjected to a synthetic non-Abelian gauge potential featuring both a magnetic field and a translationally invariant SU(2) term. We consider in particular the effect of broken time-reversal symmetry and its role in driving non-trivial topological phase transitions. By varying the spin-orbit coupling parameters, we find both a semimetal/insulator phase transition and a topological phase transition between insulating phases with different numbers of edge states. The spin is not a conserved quantity of the system and the topological phase transitions can be detected by analyzing its polarization in time of flight images, providing a clear diagnostic for the characterization of the topological phases through the partial entanglement between spin and lattice degrees of freedom.