The Fulde–Ferrell–Larkin–Ovchinnikov phase in the presence of pair hoppinginteraction

Abstract

The recent experimental support for the presence of the Fulde–Ferrell–Larkin–Ovchinnikov (FFLO)phase in CeCoIn5 directed attention towards the mechanisms responsible for this type of superconductivity.We investigate the FFLO state in a model where on-site/inter-site pairingcoexists with the repulsive pair hopping interaction. The latter interactionis interesting in that it leads to pairing with non-zero momentum of theCooper pairs even in the absence of the external magnetic field (the so-calledη pairing). It turns out that, depending on the strength of the pair hopping interaction, themagnetic field can induce one of two types of the FFLO phase with different spatialmodulations of the order parameter. It is argued that the properties of the FFLO phase maygive information about the magnitude of the pair hopping interaction. We also show thatη pairing and d-wave superconductivity may coexist in the FFLO state. It holds true also forsuperconductors which, in the absence of magnetic field, are of pure d-wave type.