Intrinsic Heating and Cooling in Adiabatic Processes for Bosons in Optical Lattices

TL;DR

Raising optical lattice depths adiabatically for bosons causes intrinsic heating due to adiabatic compression, but using blue detuned lasers for expansion can reverse this effect and achieve quantum degeneracy.

Contribution

The paper reveals the intrinsic heating mechanism during adiabatic lattice raising and proposes a method using blue detuned lasers to reverse heating and reach quantum degeneracy.

Findings

Temperature initially decreases then increases linearly with lattice height.

Intrinsic heating is caused by adiabatic compression, different from bulk heating.

Adiabatic expansion with blue detuned lasers can reduce temperature and reach degeneracy.

Abstract

We show that by raising the lattice "adiabatically" as in all current optical lattice experiments on bosons, even though the temperature may decrease initially, it will eventually rise linearly with lattice height, taking the system further away from quantum degeneracy. This increase is {\rm intrinsic} and is caused by the {\em adiabatic compression} during the raising of red detuned lattices. However, the origin of this heating, which is {\em entirely different} from that in the bulk, also shows that one can {\em reverse} the temperature rise to reach quantum degeneracy by {\em adiabatic expansion}, which can be achieved by using blue detuned lasers.