Phase Diagram of Cold Polarized Fermi Gas in Two Dimensions
Lianyi He, Pengfei Zhuang
备注：
V3: extended version according to referee's comment. 12 pages, 6 figures. Analytical results of density profile in trapped system are reported; V4: Version accepted by Physical Review A
The superfluid phase diagrams of a two-dimensional cold polarized Fermi gas in the BCS-BEC crossover are systematically and analytically investigated. In the BCS-Leggett mean field theory, the transition from unpolarized superfluid phase to normal phase is always of first order. For a homogeneous system, the two critical Zeeman fields and the critical population imbalance are analytically determined in the whole coupling parameter region, and the superfluid-normal mixed phase is shown to be the ground state between the two critical fields. The density profile in the presence of a harmonic trap calculated in the local density approximation exhibits a shell structure, a superfluid core at the center and a normal shell outside. For weak interaction, the normal shell contains a partially polarized cloud with constant density difference surrounded by a fully polarized state. For strong interaction, the normal shell is totally in fully polarized state with a density profile depending only on the global population imbalance. The di-fermion bound states can survive in the whole highly imbalanced normal phase.
Comment on "Pairing and Phase Separation in a Polarized Fermi Gas" by G. B. Partridge, W. Li, R. I. Kamar, Y. Liao, R. G. Hulet, Science 311, 503 (2006)
The evolution of an attractive polarized two-component Fermi gas at zero temperature is analyzed as its polarization is progressively decreased, from full polarization (corresponding to the polaronic limit) down to a critical polarization when superfluidity sets in. This critical polarization and the nature of the associated superfluid instability are determined within a fully self-consistent $t$-matrix approach implemented exactly at zero temperature. In this way, the polarization-vs-coupling phase diagram at zero temperature is constructed throughout the whole BCS-BEC crossover. Depending on…
We calculate the pair susceptibility of an attractive spin-polarized Fermi gas in the normal phase, as a function of the pair momentum. Close to unitarity, we find a strong enhancement of Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) pairing fluctuations over an extended region of the temperature-polarization phase diagram, which manifests itself as a pronounced peak in the pair-momentum distribution at a finite pair momentum. This peak should be amenable to experimental observation at achievable temperatures in a box-like trapping potential, as a fingerprint of FFLO pairing. Our calculations rest o…
