A novel route to a finite center-of-mass momentum pairing state; current driven FFLO state

The previously studied Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state is stabilized by a magnetic field via the Zeeman coupling in spin-singlet superconductors. Here we suggest a novel route to achieve non-zero center-of-mass momentum pairing states in superconductors with Fermi surface nesting. We investigate two-dimensional superconductors under a uniform external current, which leads to a finite pair-momentum of qe. We find that an FFLO state with a spontaneous pair momentum of qs is stabilized above a certain critical current which depends on the direction of the external current. A finite qs arises in order to make the total pair-momentum of qt(= qs + qe) perpendicular to the nesting vector, which lowers the free energy of the FFLO state, as compared to the superconducting and normal states. We also suggest experimental signatures of the FFLO state.

Hyeonjin Doh,∗  Matthew Song, and Hae-Young Kee†
Department of Physics, University of Toronto, Toronto, Ontario M5S 1A7, Canada