Pairing and superfluidity in strongly interacting Fermi gases
Name
317888939-MIT.pdf
Description
Full printable version
Size
58.45 MB
Format
Adobe PDF
Checksum (MD5)
11fbe8fd7b2067ff832cf56587b6c706
Author(s)
Schunck, Christian H. (Christian Heinrich)
Advisor(s)
Wolfgang Ketterle.
Date Issued
2008
Publisher
Massachusetts Institute of Technology
Abstract
This thesis describes experiments with superfluid spin mixtures of ultracold fermionic 6Li atoms. The properties of the strongly interacting gas are studied in the crossover regime between Bose-Einstein condensation (BEC) of two-body bound molecules and a Bardeen-Cooper-Schrieffer (BCS) superfluid of pairs bound by many-body interactions. We obtain the homogeneous phase diagram of the two -component gas with resonant interactions. As a function of temperature and spin polarization the phase diagram shows first and second order phase transitions that merge at a tricritical point. At zero temperature a first order phase transition from a superfluid with equal spin populations to a mixed normal phase is observed at a critical spin polarization known as the Chandrasekhar-Clogston limit of superfluidity. Pairing correlations in the superfluid and normal phase are studied with radio-frequency (rf) spectroscopy. A signature of strong correlations is observed above the critical temperature but also at spin polarizations where superfluidity is quenched even at zero temperature. Significant limitations for the interpretation of these experiments due to final state interactions are overcome by the creation of new superfluid spin mixtures. The asymmetric rf dissociation spectra of the new mixture allow us to determine the spectroscopic pair size in the crossover regime. The size of the resonantly interacting pairs is found to be on the order of, but smaller than the interparticle spacing. Rf spectra of the majority component in an imbalanced system show a signature of thermally excited quasiparticles and by comparison to the minority spectra reveal changes in the nature of the binding as a function of spin polarization.
Description
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2008.
Includes bibliographical references (p. 164-173).
Subjects
Physics.
MIT Department
Massachusetts Institute of Technology. Department of Physics
Terms of Use
M.I.T. theses are protected by
copyright. They may be viewed from this source for any purpose, but
reproduction or distribution in any format is prohibited without written
permission. See provided URL for inquiries about permission.
copyright. They may be viewed from this source for any purpose, but
reproduction or distribution in any format is prohibited without written
permission. See provided URL for inquiries about permission.
Persistent DSpace Link
