Massless Dirac Fermions in a Square Optical Lattice

TL;DR

This paper proposes a method to simulate massless Dirac fermions using cold atoms in a square optical lattice, enabling experimental observation of their properties and anisotropic effects.

Contribution

It introduces a novel scheme to realize and observe massless Dirac fermions in a square optical lattice with tunable anisotropic effects.

Findings

Conical points in energy spectrum indicating Dirac fermions

Anisotropic behaviors of massless Dirac fermions demonstrated

Experimental detection via Bragg spectroscopy feasible

Abstract

We propose a novel scheme to simulate and observe massless Dirac fermions with cold atoms in a square optical lattice. A U(1) adiabatic phase is created by two laser beams for the tunneling of atoms between neighbor lattice sites. Properly adjusting the tunneling phase, we find that the energy spectrum has conical points in per Brillouin zone where band crossing occurs. Near these crossing points the quasiparticles and quasiholes can be considered as massless Dirac fermions. Furthermore, the anisotropic effects of massless Dirac fermions are obtained in the present square lattice model. The Dirac fermions as well as the anisotropic behaviors realizeded in our system can be experimentally detected with the Bragg spectroscopy technique.