Lattice Thermodynamics for Ultra-Cold Atoms

TL;DR

This paper develops methods to accurately measure the temperature of ultra-cold Rb-87 gases in optical lattices, comparing experimental results with theoretical models and introducing a new approach for high-temperature regimes.

Contribution

It introduces a combined experimental and numerical approach to determine temperature in optical lattices, especially addressing limitations of bandmapping at high temperatures.

Findings

Absolute temperature measured at low temperatures using bandmapping.

Discrepancies found in high-temperature distributions via bandmapping.

In-trap size method provides reliable temperature estimates at high temperatures.

Abstract

We measure the temperature of ultra-cold Rb-87 gases transferred into an optical lattice and compare to non-interacting thermodynamics for a combined lattice--parabolic potential. Absolute temperature is determined at low temperature by fitting quasimomentum distributions obtained using bandmapping, i.e., turning off the lattice potential slowly compared with the bandgap. We show that distributions obtained at high temperature employing this technique are not quasimomentum distributions through numerical simulations. To overcome this limitation, we extract temperature using the in-trap size of the gas.