Conditions of Low Dimensionality for Strongly Interacting Atoms Under a Transverse Trap

TL;DR

This paper reveals that strongly interacting atomic gases under a transverse trap can have significant excited state populations in the ground state due to enhanced atom-molecule coupling, challenging the assumption of frozen transverse degrees of freedom.

Contribution

It demonstrates that strong interactions and induced confinement can prevent the usual low-dimensional approximation in dilute atomic gases.

Findings

Ground state includes atoms in excited transverse levels.

Enhanced atom-molecule coupling exceeds trap mode spacing.

Transverse degrees of freedom are not frozen out under strong interactions.

Abstract

For a dilute atomic gas in a strong transverse trapping potential, one normally expects that, in the ground state, the gas will populate only the lowest transverse level. We show, however, that for the strongly interacting gas under a Feshbach resonance, the ground state includes a large fraction of atoms in excited levels of the trap, even if the gas is very dilute and the trap is very strong. This is because the effective atom-molecule coupling is typically enhanced to many times the trap mode spacing by an induced confinement along the untrapped dimension(s). Thus one cannot ''freeze out'' the transverse degrees of freedom except under certain conditions.