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 on-site 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 merging 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 propose that this interaction-induced merging of Dirac points may be observed in the ultracold-Fermi-gas experiments.
- Received 3 September 2012
DOI:https://doi.org/10.1103/PhysRevA.87.053612
©2013 American Physical Society