Abstract
The possibility of a spontaneous spin-triplet paired phase of the Fulde-Ferrell-Larkin-Ovchinnikov type is studied. As it is shown in a system with the dominant interband pairing and two distinct Fermi surface sheets, the Fermi wave-vector mismatch can be compensated by a nonzero center-of-mass momentum of the Cooper pairs. This idea is examined with the use of a model which describes the two hole-like bands in the iron-based superconductor. It is shown that for the proper range of model parameters, the minima of the free energy appear which correspond to a nonzero Cooper pair momentum. Different superconducting gap symmetries are analyzed, and the corresponding phase diagrams are shown.
Highlights
The so-called Fulde-Ferrel-Larkin-Ovchinnikov (FFLO) phase has been proposed decades ago [1, 2] and attracted much attention over the years
N expresses the number of electrons per one Fe ion; the wave-vectors are given in the units of 1/a, where a is the lattice parameter; and all the energies have been normalized to the bare bandwidth W, whereas T represents the reduced temperature T ≡ kBT /W
One should note that our model with the interband pairing between the two Fermi surface sheets shown in Fig. 1a resembles the situation of one-band model with the spin-singlet pairing between the two spin subbands
Summary
The so-called Fulde-Ferrel-Larkin-Ovchinnikov (FFLO) phase has been proposed decades ago [1, 2] and attracted much attention over the years This unconventional superconducting phase can be induced by the external magnetic field in systems with high Maki parameter [3] for the case. It has been proposed by us recently The electronic structure of the system at hand should exhibit certain features to create favorable conditions for nonzero momentum pairing To study this idea, we use the interband spin-triplet pairing mechanism [13, 14] suggested for iron pnictides in [15]. One should note that our approach could be applied to other multiband systems with either spin-singlet or spin-triplet types of pairing
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