Dark state transport between unitary Fermi superfluids

TL;DR

This paper demonstrates the creation and observation of dark state transport in a strongly interacting Fermi gas, revealing how dark states can facilitate superfluid transport despite interactions and spontaneous emission effects.

Contribution

It introduces a novel method to realize and study dark states in a resonantly interacting Fermi gas, exploring their role in quantum transport and superfluidity.

Findings

Dark states enable atom transport in a strongly interacting Fermi gas.

Transport is suppressed when the dark state condition is not met due to spontaneous emission.

An asymmetry in transport timescales is observed near two-photon resonance, influenced by interactions.

Abstract

The formation of dark states is an important concept in quantum sciences, but its compatibility with strong interparticle interactions -- for example, in a quantum degenerate gas -- is hardly explored. Here, we realize a dark state in one of the spins of a two-component, resonantly interacting Fermi gas using a $\Lambda$ system within the $D_2$ transitions of $^6$Li at high magnetic field. The dark state is created in a micrometer-sized region within a one-dimensional channel connecting two superfluid reservoirs. The particle transport between the reservoirs is used as a probe. We observe that atoms are transported in the dark state and the superfluid-assisted fast current is preserved. If the dark state resonant condition is not met, the transport is suppressed by the spontaneous emission. We also uncover an asymmetry in the transport timescale across the two-photon resonance, which is absent in the non-interacting regime and diminished at higher temperatures. This work raises questions on the interplay of dark states with interparticle interactions and opens up perspectives for optical manipulation of fermionic pairing.