Origin of excess conductance of a strongly interacting gas through a constriction
In plain words
When two clouds of strongly interacting fermions are joined by a narrow channel, atoms flow through faster than the quantum limit for independent particles, even above the superfluid temperature. Pairing fluctuations are the leading explanation, but a full quantitative account is missing.
Precise statement
Two reservoirs of Li-6 near unitarity connected by a quantum point contact with a few transverse modes, as in Krinner et al. (PNAS 2016). In the normal phase near $T_c$, the particle conductance $G$ exceeds the noninteracting value $1/h$ per mode while the spin conductance is suppressed. Determine whether transport by preformed pairs (pair fluctuations) accounts quantitatively for $G$ and the spin conductance $G_s$ as functions of $T/T_F$, interaction and gate potential, and at what $T$ quantization is restored. Answer: a theory reproducing $G$ and $G_s$ within experimental error.
What would settle it
A calculation that reproduces measured $G$ and $G_s$ over temperature and interaction scans in one apparatus without fitted parameters.
Status in the literature
Pair-fluctuation transport was proposed to explain the enhancement (Liu, Zhai, Zhang, PRA 95, 013623, 2017); a parameter-free match across the full data set is not established.