Modified Fermi sphere, pairing gap, and critical temperature for the BCS-BEC crossover

Journal Article · Tue Jun 15 04:00:00 EDT 2010 · Physical Review. A

DOI:https://doi.org/10.1103/PHYSREVA.81.063619· OSTI ID:21437946

Floerchinger, S; Wetterich, C ^[1]; Scherer, M M ^[2]

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1. Institut fuer Theoretische Physik, Universitaet Heidelberg, Philosophenweg 16, D-69120 Heidelberg (Germany)
2. Theoretisch-Physikalisches Institut, Friedrich-Schiller-Universitaet Jena, Max-Wien-Platz 1, D-07743 Jena (Germany)

We investigate the phase diagram of two-component fermions in the BCS-BEC (Bose-Einstein condensate) crossover. Using functional renormalization-group equations we calculate the effect of quantum fluctuations on the fermionic self-energy parametrized by a wave-function renormalization, an effective Fermi radius, and the gap. This allows us to follow the modifications of the Fermi surface and the dispersion relation for fermionic excitations throughout the whole crossover region. We also determine the critical temperature of the second-order phase transition to superfluidity. Our results are in agreement with BCS theory including Gorkov's correction for a small negative scattering length a and with an interacting Bose gas for a small positive a. At the unitarity point the result for the gap at zero temperature agrees well with quantum Monte Carlo simulations, while the critical temperature differs.

• OSTI ID: 21437946
• Journal Information: Physical Review. A, Journal Name: Physical Review. A Journal Issue: 6 Vol. 81; ISSN 1050-2947; ISSN PLRAAN
• Country of Publication: United States
• Language: English

Related Subjects

74 ATOMIC AND MOLECULAR PHYSICS
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
BCS THEORY
BOSE-EINSTEIN CONDENSATION
BOSE-EINSTEIN GAS
CALCULATION METHODS
COMPUTERIZED SIMULATION
CORRECTIONS
CRITICAL TEMPERATURE
DIAGRAMS
DIMENSIONS
DISPERSION RELATIONS
ENERGY
ENERGY LEVELS
ENERGY-LEVEL TRANSITIONS
EXCITATION
FERMI LEVEL
FERMIONS
FLUCTUATIONS
FUNCTIONS
INFORMATION
LENGTH
MONTE CARLO METHOD
PHASE DIAGRAMS
PHASE TRANSFORMATIONS
PHYSICAL PROPERTIES
RENORMALIZATION
SCATTERING LENGTHS
SELF-ENERGY
SIMULATION
SUPERFLUIDITY
THERMODYNAMIC PROPERTIES
TRANSITION TEMPERATURE
VARIATIONS
WAVE FUNCTIONS