Adiabaticity when raising a uniform 3D optical lattice in a bimodal Bose-Einstein condensate

TL;DR

This paper investigates how to maintain adiabaticity when slowly increasing a 3D optical lattice in a two-component Bose-Einstein condensate, analyzing the coupling to excited states and deriving an analytic expression for the adiabatic time.

Contribution

It provides an analytic formula for the adiabatic time in a two-component BEC in a 3D optical lattice, considering the effects of interactions and system size.

Findings

Raising the lattice couples the ground state to two-quasiparticle excited states.

The adiabatic time depends on the atom fraction in each component.

The adiabatic time scales with system size.

Abstract

Using the time-dependent Bogoliubov approach, we study adiabaticity for a two-component Bose-Einstein condensate in a 3D time-dependent optical lattice with unit filling, in the superfluid and weakly interacting regime. We show that raising the lattice potential height can couple the ground state of the Bogoliubov Hamiltonian to excited states with two quasiparticles of opposite quasi-momenta. In the symmetric case for interactions and density in the two components these represent sound waves where the two components oscillate out of phase. We find an analytic expression of the adiabatic time, its dependence on the fraction of atoms in each component and its scaling with the system size.