Fluctuation conductivity and vortex state in a superconductor with strong paramagnetic pair breaking

The fluctuation conductivity of a moderately clean type II superconductor\nwith strong Pauli paramagnetic pair-breaking (PPB) is studied by focusing on\nthe quantum regime at low temperatures and in high magnetic fields. First, it\nis pointed out that, as the PPB effect becomes stronger, the quantum\nsuperconducting fluctuation is generally enhanced so that the Aslamasov-Larkin\n(AL) fluctuation conductivity tends to vanish upon cooling. Further, by\nexamining other (the DOS and the Maki-Thompson (MT)) terms of the fluctuation\nconductivity, the field dependence of the resulting total conductivity is found\nto depend significantly on the type of the vortex lattice (or, glass) ordered\nstate at low temperatures where the strong PPB plays important roles. By\ncomparing the present theoretical results with the fluctuation-induced negative\nmagnetoresistance behavior upon entering a PPB-induced novel SC phase of Iron\nselenide (FeSe), it is argued that the vortex matter states of the\nsuperconducting order parameter in the second lowest ($n=1$) Landau level are\nrealized in FeSe in the parallel field configuration in high fields and at low\ntemperatures\n