Spin Transport in a Mott Insulator of Ultracold Fermions

TL;DR

This paper reports the experimental observation of spin transport and diffusion in a half-filled Fermi-Hubbard model realized with ultracold fermionic atoms, revealing unconventional spin dynamics driven by super-exchange and doublon-hole tunneling.

Contribution

It demonstrates the measurement of spin transport in a strongly correlated system of ultracold atoms, providing insights into spin dynamics beyond charge transport in the Hubbard model.

Findings

Spin diffusion driven by super-exchange and doublon-hole tunneling.

Violation of the quantum limit of charge diffusion.

Technique applicable to finite doping studies.

Abstract

Strongly correlated materials are expected to feature unconventional transport properties, such that charge, spin, and heat conduction are potentially independent probes of the dynamics. In contrast to charge transport, the measurement of spin transport in such materials is highly challenging. We observed spin conduction and diffusion in a system of ultracold fermionic atoms that realizes the half-filled Fermi-Hubbard model. For strong interactions, spin diffusion is driven by super-exchange and doublon-hole-assisted tunneling, and strongly violates the quantum limit of charge diffusion. The technique developed in this work can be extended to finite doping, which can shed light on the complex interplay between spin and charge in the Hubbard model.