BCS-BEC crossover induced by a synthetic non-Abelian gauge field

Journal Article · Fri Jul 01 00:00:00 EDT 2011 · Physical Review. B, Condensed Matter and Materials Physics

DOI:https://doi.org/10.1103/PHYSREVB.84.014512· OSTI ID:21596819

Vyasanakere, Jayantha P; Shenoy, Vijay B ^[1]; Shizhong, Zhang ^[2]

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1. Centre for Condensed Matter Theory, Department of Physics, Indian Institute of Science, Bangalore 560 012 (India)
2. Department of Physics, Ohio State University, Columbus, Ohio 43210 (United States)

We investigate the ground state of interacting spin-(1/2) fermions in three dimensions at a finite density ({rho}{approx}k{sub F}{sup 3}) in the presence of a uniform non-Abelian gauge field. The gauge-field configuration (GFC) described by a vector {lambda}{identical_to}({lambda}{sub x},{lambda}{sub y},{lambda}{sub z}), whose magnitude {lambda} determines the gauge coupling strength, generates a generalized Rashba spin-orbit interaction. For a weak attractive interaction in the singlet channel described by a small negative scattering length (k{sub F}|a{sub s}| < or approx. 1), the ground state in the absence of the gauge field ({lambda}=0) is a BCS (Bardeen-Cooper-Schrieffer) superfluid with large overlapping pairs. With increasing gauge-coupling strength, a non-Abelian gauge field engenders a crossover of this BCS ground state to a BEC (Bose-Einstein condensate) of bosons even with a weak attractive interaction that fails to produce a two-body bound state in free vacuum ({lambda}=0). For large gauge couplings ({lambda}/k{sub F}>>1), the BEC attained is a condensate of bosons whose properties are solely determined by the Rashba gauge field (and not by the scattering length so long as it is nonzero)--we call these bosons ''rashbons.'' In the absence of interactions (a{sub s}=0{sup -}), the shape of the Fermi surface of the system undergoes a topological transition at a critical gauge coupling {lambda}{sub T}. For high-symmetry GFCs we show that the crossover from the BCS superfluid to the rashbon BEC occurs in the regime of {lambda} near {lambda}{sub T}. In the context of cold atomic systems, these results make an interesting suggestion of obtaining BCS-BEC crossover through a route other than tuning the interaction between the fermions.

• OSTI ID: 21596819
• Journal Information: Physical Review. B, Condensed Matter and Materials Physics, Vol. 84, Issue 1; Other Information: DOI: 10.1103/PhysRevB.84.014512; (c) 2011 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 1098-0121
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
BCS THEORY
BOSE-EINSTEIN CONDENSATION
BOUND STATE
COUPLING
DENSITY
FERMI LEVEL
FERMIONS
GROUND STATES
INTERACTIONS
L-S COUPLING
SCATTERING LENGTHS
SPIN
SUPERFLUIDITY
SYMMETRY
TWO-BODY PROBLEM
ANGULAR MOMENTUM
DIMENSIONS
ENERGY LEVELS
INTERMEDIATE COUPLING
LENGTH
MANY-BODY PROBLEM
PARTICLE PROPERTIES
PHYSICAL PROPERTIES