Coexistence of Positional and Superfluid Orders in Imbalanced Fermi Condensates

摘要

The so-called Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state is a possible inhomogeneous superfluid phase in population-imbalanced two-component Fermi gas systems. Here, a novel phase created by a population-imbalance to be called a Fermion supersolid will be proposed. In a Fermi gas with a short-ranged repulsive interaction, a positional order, corresponding to the antiferromagnetic (AFM) one in the electronic systems, may occur, although the ordinary superfluid phase usually suppresses it in population-balanced two component Fermi systems. However, we show that the coexistence between this "AFM" order and the FFLO superfluid with s-wave pairing is rather favored by the population-imbalance. This coexisting phase is the s-wave analog of the coupled AFM and FFLO orders detected in the d-wave paired superconductor CeCoIn_(5).