Quantum Liquid Crystal Phases in Fermionic Superfluids with Pairing\n between Fermion Species of Unequal Densities

Superfluidity in fermionic systems originates from pairing of fermions, and\nBose condensation of these so-called Cooper pairs. The Cooper pairs are usually\nmade of fermions of different species; for example in superconductors they are\npairs of electrons with opposite spins. Thus the most favorable situation for\npairing and superfluidity is when the two species of fermions that form pairs\nhave the same density. This paper studies the possible superfluid states when\nthe two pairing species have different densities, and show that the resultant\nstates have remarkable similarities to the phases of liquid crystals. This\nenables us to provide a unified description of the possible pairing phases, and\nunderstand the phase transitions among them.\n