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Title: Unconventional states and geometric effects in mesoscopic systems of ultra-cold atomic Fermi gases

During the last decade, experiments all over the world started to test the superconducting state of matter using a newly developed mesoscopic tunable system: trapped ultra-cold atomic gases. Theorists and experimentalists hand-in-hand are now able to advance our understanding of the superconducting state by asking new questions that probe further into the physical mechanisms underlying the phenomenon and the door is open to the exploration of exotic unconventional superconducting states. In particular, a series of experiments on systems of trapped cold atomic gases were aimed at studying the effects of polarization on superconducting pairing. Two different experimental groups encountered surprising qualitative and quantitative discrepancies which seemed to be a function of the confining geometry and the cooling protocol. Our numerical studies demonstrate a tendency towards metastability and suggest an explanation for the observed discrepancy. From our calculations, the most likely solution which is consistent with the experiments supports a state strikingly similar to the so called FFLO state (after Ferrell, Fulde, Larkin and Ovchinnikov), which had been theorized long ago but eluded detection so far. Moreover, the three-dimensional scenario described above is reminiscent of predictions for one-dimensional systems of dilute polarized attractive gases and another set of ultra-cold-atom experiments incorporatesmore » optical lattices to study this reduced-dimensionality setting. The measurements are in quantitative agreement with theoretical calculations (using a wide array of numerical and analytic techniques) in which a partially polarized phase is found to be the one-dimensional analogue of the FFLO state. Moreover, exploring the dimensional-crossover regime, our latest findings indicate that the mesoscopic nature of these quasi-one-dimensional systems favors the appearance of a new type of Mott phase transition involving an emergent pair-superfluid of equal-spin fermions.« less
Authors:
 [1]
  1. Physics Department, University of Cincinnati, Cincinnati, OH 45221-0011 (United States)
Publication Date:
OSTI Identifier:
22307991
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Conference Proceedings; Journal Volume: 1619; Journal Issue: 1; Conference: 4. conference on nuclei and mesoscopic physics 2014, East Lansing, MI (United States), 5-9 May 2014; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; ATOMS; FERMI GAS; FERMIONS; MATHEMATICAL SOLUTIONS; NUMERICAL ANALYSIS; ONE-DIMENSIONAL CALCULATIONS; PHASE TRANSFORMATIONS; POLARIZATION; SPIN; SUPERCONDUCTIVITY; SUPERCONDUCTORS; SUPERFLUIDITY; THREE-DIMENSIONAL CALCULATIONS; TRAPPING