Flat bands, Dirac cones and atom dynamics in an optical lattice

TL;DR

This paper investigates atom dynamics in an optical lattice with flat bands and Dirac cones, revealing distinct behaviors for fermions and bosons and highlighting limitations of mean field models for bosonic systems.

Contribution

It demonstrates how flat bands and Dirac cones influence atom dynamics in optical lattices and compares fermionic and bosonic responses using exact methods.

Findings

Fermions lose atoms in Dirac cones when confinement is removed.

Flat band atoms remain immobile under certain conditions.

Mean field models are inadequate for bosonic atom dynamics.

Abstract

We study atoms trapped with a harmonic confinement in an optical lattice characterized by a flat band and Dirac cones. We show that such an optical lattice can be constructed which can be accurately described with the tight binding or Hubbard models. In the case of fermions the release of the harmonic confinement removes fast atoms occupying the Dirac cones while those occupying the flat band remain immobile. Using exact diagonalization and dynamics we demonstrate that a similar strong occupation of the flat band does not happen in bosonic case and furthermore that the mean field model is not capable for describing the dynamics of the boson cloud.