Tunneling transport of strongly interacting Fermi gases across the superfluid transition

Tunneling transport measurements provide a powerful tool to unveil both the coherence properties of a many-body system, through the celebrated Josephson effect, and the role of excitations in its conduction dynamics.Here I present our results in probing condensation of strongly interacting fermionic superfluids, by injecting controlled currents in an ultracold atom two-reservoirs system weakly-coupled through a tunable tunneling barrier. In the absence of any applied chemical potential difference, we directly measure Josephson supercurrents, that depend sinusoidally on the relative phase. By comparing the measured Josephson critical current throughout the BEC-BCS crossover with an analytic model, we extract the condensed fraction of fermionic superfluids.Moreover, we characterize the operation of an atomic junction at unitarity across the superfluid transition. We find Josephson supercurrents to vanish when approaching the critical temperature due to condensate depletion. Remarkably, we observe the condensate to contribute also to resistive currents. In contrast with superconducting junctions, we detect a large anomalous normal conductance at low temperature, arising from the coherent coupling between the condensate and Bogoliubov-Anderson phonons.Our work highlights the key role of transport measurements to disclose the nature of quantum materials.