Observation of Elastic Doublon Decay in the Fermi-Hubbard Model

TL;DR

This study observes how highly excited doublon states decay in a three-dimensional Fermi-Hubbard system, revealing an exponential dependence of their lifetime on the interaction-to-kinetic energy ratio, supported by many-body calculations.

Contribution

It provides the first detailed experimental measurement of doublon decay times in a 3D optical lattice and confirms the decay mechanism through diagrammatic many-body calculations.

Findings

Doublon lifetime varies exponentially with U/J ratio.

Decay mechanism involves high-order scattering processes.

Good agreement between experimental data and theoretical calculations.

Abstract

We investigate the decay of highly excited states of ultracold fermions in a three-dimensional optical lattice. Starting from a repulsive Fermi-Hubbard system near half filling, we generate additional doubly occupied sites (doublons) by lattice modulation. The subsequent relaxation back to thermal equilibrium is monitored over time. The measured doublon lifetime covers two orders of magnitude. In units of the tunneling time h/J it is found to depend exponentially on the ratio of on-site interaction energy U to kinetic energy J. We argue that the dominant mechanism for the relaxation is a high order scattering process involving several single fermions as scattering partners. A many-body calculation is carried out using diagrammatic methods, yielding good agreement with the data.