Observation of pseudogap behavior in a strongly interacting Fermi gas
Abstract
Ultracold atomic Fermi gases present an opportunity to study strongly interacting Fermi systems in a controlled and uncomplicated setting. The ability to tune attractive interactions has led to the discovery of superfluidity in these systems with an extremely high transition temperature, near T/T_F = 0.2. This superfluidity is the electrically neutral analog of superconductivity; however, superfluidity in atomic Fermi gases occurs in the limit of strong interactions and defies a conventional BCS description. For these strong interactions, it is predicted that the onset of pairing and superfluidity can occur at different temperatures. This gives rise to a pseudogap region where, for a range of temperatures, the system retains some of the characteristics of the superfluid phase, such as a BCS-like dispersion and a partially gapped density of states, but does not exhibit superfluidity. By making two independent measurements: the direct observation of pair condensation in momentum space and a measurement of the single-particle spectral function using an analog to photoemission spectroscopy, we directly probe the pseudogap phase. Our measurements reveal a BCS-like dispersion with back-bending near the Fermi wave vector k_F that persists well above the transition temperature for pair condensation.
Keywords
Cite
@article{arxiv.1003.1147,
title = {Observation of pseudogap behavior in a strongly interacting Fermi gas},
author = {J. P. Gaebler and J. T. Stewart and T. E. Drake and D. S. Jin and A. Perali and P. Pieri and G. C. Strinati},
journal= {arXiv preprint arXiv:1003.1147},
year = {2010}
}