Vortex Lattice Melting Line in Superconductors with Paramagnetic Pair-Breaking

TL;DR

This paper theoretically investigates the vortex lattice melting line in superconductors with strong paramagnetic pair-breaking, focusing on FeSe, and finds that the FFLO state influences the vortex liquid regime and phase diagram.

Contribution

It provides a theoretical analysis of the vortex lattice melting curve in superconductors with strong PPB and FFLO states, clarifying their effects on the phase diagram.

Findings

PPB narrows the vortex liquid regime

Vortex liquid shrinks near the FFLO stability region

Phase diagrams of FeSe are discussed in different field orientations

Abstract

Recent experiments on the Iron-based superconductor FeSe in a high magnetic field have suggested the presence of both the fluctuation-induced vortex liquid regime and a Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) vortex lattice. To get a general picture on the magnetic phase diagram in type II superconductors with strong superconducting (SC) fluctuation and strong paramagnetic pair-breaking (PPB) such as FeSe, the vortex lattice melting curve Hm(T) is theoretically investigated in the situations where a FFLO state is expected to occur. In general, the PPB tends to narrow the vortex liquid regime intervening between Hc2(T) and Hm(T). In particular, the vortex liquid regime is found to rapidly shrink upon entering, by cooling, the temperature range in which the FFLO state with a periodic modulation parallel to the magnetic field is stable in the mean field theory. Based on the present results, the high field SC phase diagrams of FeSe in the parallel and perpendicular field configurations are discussed.