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BCS-BEC crossover in bilayers of cold fermionic polar molecules

Zinner, N. T. and Wunsch, B. and Pekker, D. and Wang, D.-W. (2012) BCS-BEC crossover in bilayers of cold fermionic polar molecules. Physical Review A, 85 (1). Art. No. 013603. ISSN 1050-2947. doi:10.1103/PhysRevA.85.013603.

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We investigate the quantum and thermal phase diagram of fermionic polar molecules loaded in a bilayer trapping potential with perpendicular dipole moment. We use both a BCS-theory approach that is most reliable at weak coupling and a strong-coupling approach that considers the two-body bound dimer states with one molecule in each layer as the relevant degree of freedom. The system ground state is a Bose-Einstein condensate (BEC) of dimer bound states in the low-density limit and a paired superfluid (BCS) state in the high-density limit. At zero temperature, the intralayer repulsion is found to broaden the regime of BCS-BEC crossover and can potentially induce system collapse through the softening of roton excitations. The BCS theory and the strongly coupled dimer picture yield similar predictions for the parameters of the crossover regime. The Berezinskii-Kosterlitz-Thouless transition temperature of the dimer superfluid is also calculated. The crossover can be driven by many-body effects and is strongly affected by the intralayer interaction which was ignored in previous studies.

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Additional Information:© 2012 American Physical Society. Received 10 September 2010; revised manuscript received 10 February 2011; published 3 January 2012. We thank E. Demler, L. Pollet, A. S. Jensen, G. M. Bruun, and M. M. Parish for fruitful discussions and C.-H. Lin and I.-W. Tsai for early pioneering work. D.W.W. appreciates the hospitality of the JQI during the initial investigation of this project and acknowledges research and travel support from NCTS (Taiwan). Support by the Carlsberg Foundation and by the German Science Foundation under Grant No.WU 609/1-1 is gratefully acknowledged.
Funding AgencyGrant Number
Carlsberg FoundationUNSPECIFIED
German Science FoundationWU 609/1-1
Issue or Number:1
Classification Code:PACS: 67.85.-d, 03.75.Ss, 74.78.-w
Record Number:CaltechAUTHORS:20120206-133047555
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:29155
Deposited By: Tony Diaz
Deposited On:01 Mar 2012 20:40
Last Modified:09 Nov 2021 17:04

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