Scientific Results

Tunneling Transport of Unitary Fermions across the Superfluid Transition

Year: 2021

Authors: Del Pace G., Kwon W. J., Zaccanti M., Roati G., Scazza F.

Autors Affiliation: Department of Physics and Astronomy, University of Florence, 50019 Sesto Fiorentino, Italy
European Laboratory for Nonlinear Spectroscopy (LENS), 50019 Sesto Fiorentino, Italy
Istituto Nazionale di Ottica del Consiglio Nazionale delle Ricerche (CNR-INO), 50019 Sesto Fiorentino, Italy

Abstract: We investigate the transport of a Fermi gas with unitarity-limited interactions across the superfluid phase transition, probing its response to a direct current (dc) drive through a tunnel junction. As the superfluid critical temperature is crossed from below, we observe the evolution from a highly nonlinear to an Ohmic conduction characteristic, associated with the critical breakdown of the Josephson dc current induced by pair condensate depletion. Moreover, we reveal a large and dominant anomalous contribution to resistive currents, which reaches its maximum at the lowest attained temperature, fostered by the tunnel coupling between the condensate and phononic Bogoliubov-Anderson excitations. Increasing the temperature, while the zeroing of supercurrents marks the transition to the normal phase, the conductance drops considerably but remains much larger than that of a normal, uncorrelated Fermi gas tunneling through the same junction. We attribute such enhanced transport to incoherent tunneling of sound modes, which remain weakly damped in the collisional hydrodynamic fluid of unpaired fermions at unitarity.

Journal/Review: PHYSICAL REVIEW LETTERS

Volume: 126      Pages from: 055301  to: 055301

KeyWords: Fermi gases, Fermionic condensates, Josephson effect, Quantum transport, Quasiparticles & collective excitations, Superfluidity, Transport phenomena, Tunnel junctions
DOI: 10.1103/PhysRevLett.126.055301

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