High-Field Pauli-Limiting Behavior and Strongly Enhanced Upper Critical Magnetic Fields near the Transition Temperature of an Arsenic-Deficient LaO_0.9F_0.1FeAs_(1-\delta) Superconductor

TL;DR

This study investigates the high-field behavior of an arsenic-deficient LaO_0.9F_0.1FeAs_(1-elta) superconductor, revealing Pauli-limited upper critical fields near the transition temperature and the effects of disorder on superconductivity.

Contribution

It provides detailed measurements of the upper critical field in a disordered superconductor, highlighting Pauli-limiting effects and the impact of arsenic deficiency on superconducting properties.

Findings

Upper critical field Bc2(T) reaches about 63-68 T at low temperatures.

B_c2(T) shows flattening near 23 K indicating Pauli-limited behavior.

Disorder effects influence the superconducting pairing mechanisms.

Abstract

We report upper critical field B_c2(T) data for disordered (arsenic-deficient) LaO_0.9F_0.1FeAs_(1-delta) in a wide temperature and magnetic field range up to 47 T. Because of the large linear slope of Bc2 about -5.4 T/K to -6.6 T/K near Tc = 28.5 K the T-dependence of the in-plane Bc2(T) shows a flattening near 23 K above 30 T which points to Pauli-limited behavior with Bc2(0) about 63-68 T. Our results are discussed in terms of disorder effects within conventional and unconventional superconducting pairings.