BCS-BEC crossover and quantum phase transition for 6Li and 40K atoms across Feshbach resonance

Abstract

We systematically study the BCS-BEC crossover and the quantum phase transition in ultracold 6Li and 40K atoms across a wide Feshbach resonance. The background scattering lengths for 6Li and 40K have opposite signs, which lead to very different behaviors for these two types of atoms. For 40K, both the two-body and the many-body calculations show that the system always has two branches of solutions: one corresponds to a deeply bound molecule state; and the other, the one accessed by the current experiments, corresponds to a weakly bound state with population always dominantly in the open channel. For 6Li, there is only a unique solution with the standard crossover from the weakly bound Cooper pairs to the deeply bound molecules as one sweeps the magnetic field through the crossover region. Because of this difference, for the experimentally accessible state of 40K, there is a quantum phase transition at zero temperature from the superfluid to the normal fermi gas at the positive detuning of the magnetic field where the s-wave scattering length passes its zero point. For 6Li, however, the system changes continuously across the zero point of the scattering length. For both types of atoms, we also give detailed comparison between the results from the two-channel and the single-channel model over the whole region of the magnetic field detuning.

7 pages, 6 figures

References in corpus (3)

• Vortices and Superfluidity in a Strongly Interacting Fermi Gas
• Observation of the Pairing Gap in a Strongly Interacting Fermi Gas
• Molecular Probe of Pairing in the BEC-BCS Crossover

Cited by in corpus (9)

• Finite temperature phase diagram of a spin-polarized ultracold Fermi gas in a highly elongated harmonic trap
• Superfluidity at the BEC-BCS crossover in two-dimensional Fermi gases with population and mass imbalance
• Phase diagram of a polarized Fermi gas across a Feshbach resonance in a potential trap
• Conditions of Low Dimensionality for Strongly Interacting Atoms Under a Transverse Trap
• Finite temperature phase diagram of trapped Fermi gases with population imbalance
• Role of Particle Interactions in the Feshbach Conversion of Fermion Atoms to Bosonic Molecules
• Probing Fermionic Condensates by Fast-Sweep Projection onto Feshbach Molecules
• BCS-BEC crossover and quantum phase transition in an ultracold Fermi gas under spin-orbit coupling
• Significance of dressed molecules in a quasi-two-dimensional polarized Fermi gas