Interaction-Assisted Reversal of Thermopower with Ultracold Atoms

TL;DR

This study investigates thermoelectric currents in ultracold fermionic atoms, demonstrating how interactions can reverse current direction and offering insights into heat and spin coupling in strongly correlated quantum systems.

Contribution

It reveals how strong interactions can reverse thermoelectric current direction in ultracold atoms, advancing understanding of heat transport in quantum many-body systems.

Findings

Thermoelectric currents can be controlled via optical potentials.

Strong interactions reverse the current direction.

Modeling aligns with non-interacting case and explains interaction effects.

Abstract

We study thermoelectric currents of neutral, fermionic atoms flowing through a mesoscopic channel connecting a hot and a cold reservoir across the superfluid transition. The thermoelectric response results from a competition between density-driven diffusion from the cold to the hot reservoir and the channel favoring transport of energetic particles from hot to cold. We control the relative strength of both contributions to the thermoelectric response using an external optical potential in a nearly non-interacting and a strongly-interacting system. Without interactions, the magnitude of the particle current can be tuned over a broad range but is restricted to flow from hot to cold in our parameter regime. Strikingly, strong interparticle interactions additionally reverse the direction of the current. We quantitatively model ab initio the non-interacting observations and qualitatively explain the interaction-assisted reversal by the reduction of entropy transport due to pairing correlations. Our work paves the way to studying the coupling of spin and heat in strongly correlated matter using spin-dependent optical techniques with cold atoms.