Universal behavior of the upper critical field in iron based superconductors

TL;DR

This paper reviews the universal high upper critical fields and weak anisotropy in iron-based superconductors, highlighting their potential applications and discussing pair-breaking mechanisms in high magnetic fields.

Contribution

It provides a comprehensive review of the upper critical field behavior and anisotropy in iron-based superconductors, emphasizing their unique properties among layered superconductors.

Findings

All FeSCs have extremely large upper critical fields.

FeSCs exhibit weak anisotropy despite layered structures.

Potential for future applications due to these properties.

Abstract

The newly discovered iron-based high temperature superconductors have demonstrated rich physical properties. Here we give a brief review on the recent studies of the upper critical field and its anisotropy in a few typical series of the iron-based superconductors (FeSCs). In spite of their characters of a layered crystal structure, all the FeSCs possess an extremely large upper critical field and a weak anisotropy of superconductivity, being unique among the layered superconductors. These particular properties indicate potential applications of the FeSCs in the future. Based on the experimental facts of the FeSCs, we will discuss the possible mechanisms of pair breaking in high magnetic fields and its restrictions on the theoretical analysis of the superconducting pairing mechanisms.