Temperature dependence of the contact in a unitary Fermi gas

Ultracold gases of fermionic atoms can display remarkable properties such as superfluidity which involves atoms pairing up to flow with zero resistance. This pairing is notoriously challenging to model theoretically, particularly when the interactions between atoms is strong. Recently, however, an important breakthrough was made via the introduction of a parameter known as the contact, which describes the likelihood of finding two particles at very small separation. The contact parameter depends on both the temperature of the system and the strength of the interactions between particles.

Researchers at Swinburne's Centre for Atom-Optics and Ultrafast Spectroscopy have recently made the first experimental measurements of the temperature dependence of the contact in a unitary Fermi gas of ultracold atoms using Bragg spectroscopy. This work shows for the first time how short-range pair correlations in these strongly interacting gases build up steadily as the temperature is lowered and are present even before the gas enters the superfluid regime, in agreement with theoretical predictions. The work has been published in Physical Review Letters.

Link to paper: E.D. Kuhnle et al., Phys. Rev. Lett. 106, 170402 (2011) arxiv 1012.2626