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Temperature dependence of the contact in a unitary Fermi gas
April, 2011
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
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