Interaction induced mergence of Dirac points in Non-Abelian optical lattices

TL;DR

This paper investigates how strong on-site interactions in a non-Abelian optical lattice cause Dirac points in the energy spectrum of ultracold Fermi gases to merge, leading to a quantum phase transition.

Contribution

It demonstrates that interactions induce the merging of Dirac points, revealing a controllable quantum phase transition in ultracold Fermi gases with non-Abelian gauge fields.

Findings

Dirac points remain stable under weak interactions.

Strong interactions cause Dirac points to merge into a hybrid point.

Merging indicates a transition from semimetallic to insulating phase.

Abstract

We study the properties of an ultracold Fermi gas loaded in a square optical lattice and subjected to an external and classical non-Abelian gauge field. We calculate the energy spectrum of the system and show that the Dirac points in the energy spectrum will remain quite stable under onsite interaction of certain strength. Once the on-site interaction grows stronger than a critical value, the Dirac points will no longer be stable and merge into a single hybrid point. This mergence implies a quantum phase transition from a semimetallic phase to a band insulator. The on-site interaction between ultracold fermions could be conveniently controlled by Feshbach resonances in current experiments. We proposed that this remarkable interaction induced mergence of Dirac points may be observed in the ultracold fermi gas experiments.