• Open Access

Interaction-Assisted Reversal of Thermopower with Ultracold Atoms

Samuel Häusler, Philipp Fabritius, Jeffrey Mohan, Martin Lebrat, Laura Corman, and Tilman Esslinger
Phys. Rev. X 11, 021034 – Published 13 May 2021

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 noninteracting 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 noninteracting 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.

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  • Received 2 October 2020
  • Accepted 18 February 2021

DOI:https://doi.org/10.1103/PhysRevX.11.021034

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.

Published by the American Physical Society

Physics Subject Headings (PhySH)

Atomic, Molecular & Optical

Authors & Affiliations

Samuel Häusler1, Philipp Fabritius1, Jeffrey Mohan1, Martin Lebrat2, Laura Corman1,*,†, and Tilman Esslinger1,‡

  • 1Department of Physics, ETH Zurich, 8093 Zurich, Switzerland
  • 2Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA

  • *lauracorman@xrite.com
  • Present address: X-Rite Europe GmbH, 8150 Regensdorf, Switzerland.
  • esslinger@phys.ethz.ch

Popular Summary

In materials, heat and electrical currents are often intertwined, with their interplay giving rise to thermoelectric effects. This coupling not only contains signatures of some fundamental physics but also is of great interest in various applications, allowing one to convert heat into electricity or to refrigerate with an electrical current. In our work, we engineer and control the strength of the coupling between charge and heat currents induced in a synthetic device made of cold atoms.

Without interatomic interactions, particles in our device contribute independently to the resulting thermoelectric current with a magnitude we can tune over a large range. By turning on strongly attractive interactions, we enhance and even reverse the direction of this current.

Fundamentally, we attribute the interaction-assisted reversal to a reduction in entropy transport due to correlations that arise in a phase of matter that is challenging to understand. From a practical point of view, the enhanced coupling underlines that interparticle interactions are relevant to improve the efficiency of the thermoelectric conversion. Moreover, we smoothly turn our system from a heat engine into a heat pump, the latter of which is an important ingredient to further cool quantum gases.

Our work paves the way to studying the coupling of heat and spin in strongly correlated matter using spin-dependent optical techniques with cold atoms.

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Vol. 11, Iss. 2 — April - June 2021

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