High field superconducting phase diagrams including Fulde-Ferrell-Larkin-Ovchinnikov vortex states

TL;DR

This paper systematically studies the superconducting phase diagrams of quasi-2D superconductors, revealing how impurity levels and magnetic field orientation influence the emergence of FFLO vortex states and their distinct characteristics.

Contribution

It introduces a theoretical framework for understanding FFLO vortex states in Q2D superconductors, emphasizing the role of impurities and magnetic field direction.

Findings

High field superconducting state differs from FFLO modulating along the field.

Weak impurities suppress certain FFLO vortex states.

Phase diagrams vary significantly with magnetic field orientation.

Abstract

Motivated by a striking observation of a Fulde-Ferell-Larkin-Ovchinnikov (FFLO) vortex state in the heavy fermion material CeCoIn5 in fields {\it perpendicular} to the superconducting planes (${\bf H} \parallel c$), superconducting phase diagrams including an FFLO state of quasi two-dimensional (Q2D) superconductors are systematically studied. In the clean {\it limit}, the high field superconducting state in the low temperature limit should be not the FFLO state modulating along ${\bf H}$, appeared in CeCoIn5 in both ${\bf H} \parallel c$ and ${\bf H} \perp c$, but a different vortex state with a modulation, induced by the paramagnetism, perpendicular to the field. It is found that the presence of weak impurities is the origin of the absence in CeCoIn5 of the latter state and leads to the ${\bf H} \parallel c$ phase diagram, as seen in CeCoIn5, {\it apparently} different in character from that in ${\bf H} \perp c$.