Swallowtail Band Structure of the Superfluid Fermi Gas in an Optical Lattice

Year: 2011

Authors: Watanabe G., Yoon S., Dalfovo F.

Autors Affiliation: Asia Pacific Center for Theoretical Physics (APCTP), Pohang, Gyeongbuk 790-784, Korea; Department of Physics, POSTECH, Pohang, Gyeongbuk 790-784, Korea; Nishina Center, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan; INO-CNR BEC Center and Department of Physics, University of Trento, 38123 Povo, Italy

Abstract: We investigate the energy band structure of the superfluid flow of ultracold dilute Fermi gases in a one-dimensional optical lattice along the BCS to Bose-Einstein condensate (BEC) crossover within a mean-field approach. In each side of the crossover region, a loop structure (swallowtail) appears in the Bloch energy band of the superfluid above a critical value of the interaction strength. The width of the swallowtail is largest near unitarity. Across the critical value of the interaction strength, the profiles of density and pairing field change more drastically in the BCS side than in the BEC side. It is found that along with the appearance of the swallowtail, there exists a narrow band in the quasiparticle energy spectrum close to the chemical potential, and the incompressibility of the Fermi gas consequently experiences a profound dip in the BCS side, unlike in the BEC side.


Volume: 107 (27)      Pages from: 270404  to: 270404

More Information: We acknowledge C. J. Pethick, Y. Shin, and T. Takimoto for helpful discussions. This work was supported by the Max Planck Society, the Korea Ministry of Education, Science and Technology, Gyeongsangbuk-Do, Pohang City, for the support of the JRG at APCTP, and ERC through the QGBE grant. Calculations were performed on RICC in RIKEN and Wiglaf at the University of Trento.
DOI: 10.1103/PhysRevLett.107.270404

Citations: 15
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