Evolution of condensate fraction during rapid lattice ramps

TL;DR

This study combines experiments and simulations to show that rapid lattice ramps cause significant momentum redistribution in interacting atomic gases, challenging the validity of bandmapping as an equilibrium probe.

Contribution

It reveals how interactions induce momentum redistribution during rapid lattice ramps, highlighting the role of particle-hole excitations and invalidating previous assumptions about adiabaticity.

Findings

Interactions cause rapid momentum redistribution within milliseconds.

Bandmapping is not reliable as an equilibrium probe in interacting gases.

Low-momentum particle-hole excitations drive the redistribution process.

Abstract

Combining experiments and numerical simulations, we investigate the redistribution of quasi-momentum in a gas of atoms trapped in an optical lattice when the lattice depth is rapidly reduced. We find that interactions lead to significant momentum redistribution on millisecond timescales, thereby invalidating previous assumptions regarding adiabaticity. We show that this phenomenon is driven by the presence of low-momentum particle-hole excitations in an interacting system. Our results invalidate bandmapping as an equilibrium probe in interacting gases.