We investigate the crossover from BCS pairing to molecular Bose-Einstein condensation (BEC) in an atomic gas with two fermion species with masses ${m}_{\ensuremath{\uparrow}}\ensuremath{\ne}{m}_{\ensuremath{\downarrow}}$ tuned through a Feshbach resonance. We present results for the $T=0$ equation of state as a function of the scattering length including the effects of Gaussian fluctuations about the mean field ground state. We compute the ground state energy as a function of ${m}_{\ensuremath{\uparrow}}/{m}_{\ensuremath{\downarrow}}$ at unitarity and find excellent agreement with the quantum Monte Carlo result for ${m}_{\ensuremath{\uparrow}}/{m}_{\ensuremath{\downarrow}}=6.67$ for a $^{40}\mathrm{K}$ - $^{6}\mathrm{Li}$ mixture. We show that the dimer scattering length in the BEC limit as a function of ${m}_{\ensuremath{\uparrow}}/{m}_{\ensuremath{\downarrow}}$ compares well with the exact four-body results of Petrov et al. [J. Phys. B 38, S645 (2005)]. We also derive the condition for trapping frequencies to obtain an unpolarized gas in a harmonic trap.We investigate the crossover from BCS pairing to molecular Bose-Einstein condensation (BEC) in an atomic gas with two fermion species with masses ${m}_{\ensuremath{\uparrow}}\ensuremath{\ne}{m}_{\ensuremath{\downarrow}}$ tuned through a Feshbach resonance. We present results for the $T=0$ equation of state as a function of the scattering length including the effects of Gaussian fluctuations about the mean field ground state. We compute the ground state energy as a function of ${m}_{\ensuremath{\uparrow}}/{m}_{\ensuremath{\downarrow}}$ at unitarity and find excellent agreement with the quantum Monte Carlo result for ${m}_{\ensuremath{\uparrow}}/{m}_{\ensuremath{\downarrow}}=6.67$ for a $^{40}\mathrm{K}$-$^{6}\mathrm{Li}$ mixture. We show that the dimer scattering length in the BEC limit as a function of ${m}_{\ensuremath{\uparrow}}/{m}_{\ensuremath{\downarrow}}$ compares well with the exact four-body results of Petrov et al. [J. Phys. B 38, S645 (2005)]. We also derive the condition for trapping frequencies to obtain an unpolarized gas in a harmonic trap.

arXiv:0906.4300Physical Review AMar 15, 201019 citations

Quantum fluctuations in the superfluid state of the BCS-BEC crossover

Rajdeep Sensarma, Roberto B. Diener, Mohit Randeria

Bulletin of the American Physical SocietyMar 6, 20070 citations

Quantum Monte Carlo study of a Fermi gas in the BCS-BEC crossover

S. Giorgini

Bulletin of the American Physical SocietyMar 23, 20050 citations

BCS-BEC crossover in a two-band superconductor with odd-parity hybridization

G. N. Bremm, M. A. Contínentino, Tobias Micklitz

We study the crossover from the weak coupling Bardeen-Cooper-Schrieffer (BCS) state to Bose-Einstein condensation (BEC) at strong coupling in a two-band superconductor with orbitals of opposite parity coexisting at a common Fermi surface in the metallic state. In such systems hybridization can play a role similar to spin-orbit interaction in fermionic spinor gases, enhancing interband pairing and opening the possibility for driving the BCS-BEC crossover. Building on a mean-field analysis, we investigate the BCS-BEC crossover induced by a variation of the hybridization strength. We show that the relevant scale for the crossover depends strongly on the ratio of effective masses, with the crossover favored in systems with one dispersive and one flat band. Including the effect of thermal pair fluctuations in a one-loop approximation, we calculate the dependence of the critical temperature on the microscopic parameters in the strong coupling regime.We study the crossover from the weak coupling Bardeen-Cooper-Schrieffer (BCS) state to Bose-Einstein condensation (BEC) at strong coupling in a two-band superconductor with orbitals of opposite parity coexisting at a common Fermi surface in the metallic state. In such systems hybridization can play a role similar to spin-orbit interaction in fermionic spinor gases, enhancing interband pairing and opening the possibility for driving the BCS-BEC crossover. Building on a mean-field analysis, we investigate the BCS-BEC crossover induced by a variation of the hybridization strength. We show that the relevant scale for the crossover depends strongly on the ratio of effective masses, with the crossover favored in systems with one dispersive and one flat band. Including the effect of thermal pair fluctuations in a one-loop approximation, we calculate the dependence of the critical temperature on the microscopic parameters in the strong coupling regime.

Physical review. B./Physical review. BSep 16, 20214 citations

Fermion Pairing and BEC-BCS Crossover in Novel Systems

Renyuan Liao

Jan 1, 20080 citations

T=0

equation of state as a function of the scattering length including the effects of Gaussian fluctuations about the mean field ground state. We compute the ground state energy as a function of ${m}_{\ensuremath{\uparrow}}/{m}_{\ensuremath{\downarrow}}$ at unitarity and find excellent agreement with the quantum Monte Carlo result for ${m}_{\ensuremath{\uparrow}}/{m}_{\ensuremath{\downarrow}}=6.67$ for a

^{40}\mathrm{K}

^{6}\mathrm{Li}

mixture. We show that the dimer scattering length in the BEC limit as a function of ${m}_{\ensuremath{\uparrow}}/{m}_{\ensuremath{\downarrow}}$ compares well with the exact four-body results of Petrov et al. [J. Phys. B 38, S645 (2005)]. We also derive the condition for trapping frequencies to obtain an unpolarized gas in a harmonic trap.