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Pairing in ultracold Fermi gases in the lowest Landau level

Möller, Gunnar, Jolicoeur, Th, Regnault, N (2009) Pairing in ultracold Fermi gases in the lowest Landau level. Physical Review A, 79 (3). ISSN 1050-2947. E-ISSN 1094-1622. (doi:10.1103/PhysRevA.79.033609) (KAR id:55559)

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We study a rapidly rotating gas of unpolarized spin-1/2 ultracold fermions in the two-dimensional regime when all atoms reside in the lowest Landau level. Due to the presence of the spin degree of freedom both s-wave and p-wave interactions are allowed at ultralow temperatures. We investigate the phase diagram of this system as a function of the filling factor in the lowest Landau level and in terms of the ratio between s- and p-wave interaction strengths. We show that the presence of attractive interactions induces a wide regime of phase separation with formation of maximally compact droplets that are either fully polarized or composed of spin-singlets. In the regime with no phase separation, we give evidence for fractional quantum Hall states. Most notably, we find two distinct singlet states at the filling nu=2/3 for different interactions. One of these states is accounted for by the composite fermion theory, while the other one is a paired state for which we identify two competing descriptions with different topological structures. This paired state may be an Abelian liquid of composite spin-singlet Bose molecules with Laughlin correlations. Alternatively, it may be a known non-Abelian paired state, indicated by good overlaps with the corresponding trial wave function. By fine tuning of the scattering lengths it is possible to create the non-Abelian critical Haldane-Rezayi state for nu = 1/2 and the permanent state of Moore and Read for nu=1. For purely repulsive interactions, we also find evidence for a gapped Halperin state at nu=2/5.

Item Type: Article
DOI/Identification number: 10.1103/PhysRevA.79.033609
Uncontrolled keywords: Physics of Quantum Materials
Subjects: Q Science > QC Physics > QC173.45 Condensed Matter
Divisions: Faculties > Sciences > School of Physical Sciences > Functional Materials Group
Depositing User: Gunnar Moeller
Date Deposited: 05 Dec 2017 14:47 UTC
Last Modified: 05 Jul 2019 10:38 UTC
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