The role of interactions, tunneling and harmonic confinement on the adiabatic loading of bosons in an optical lattice

TL;DR

This paper investigates how interactions, tunneling, and harmonic confinement influence the adiabatic loading process of bosons in optical lattices, revealing conditions that can lead to heating or cooling during the process.

Contribution

It provides a detailed analysis of entropy-temperature relations for interacting bosons in optical lattices, highlighting the effects of tunneling and trapping on temperature changes during adiabatic loading.

Findings

Finite tunneling reduces heating during adiabatic loading.

Harmonic confinement can lower the final temperature due to superfluid components.

Interactions can induce heating, contrasting with non-interacting bosons.

Abstract

We calculate entropy-temperature curves for interacting bosons in unit filled optical lattices for both homogeneous and harmonically trapped situations, and use them to understand how adiabatic changes in the lattice depth affect the temperature of the system. In a translationally invariant lattice, the zero tunneling limit facilitates a rather detailed analytic description. Unlike the non-interacting bosonic system which is always cooled upon adiabatic loading for low enough initial temperature, the change in the excitation spectrum induced by interactions can lead to heating. Finite tunneling helps to reduce this heating. Finally, we study the spatially inhomogeneous system confined in a parabolic potential and show that the presence of the trap can significantly reduce the final available temperature, due to the non-vanishing superfluid component at the edge of the cloud which is present in trapped systems.