Upper critical field, penetration depth, and depinning frequency of the novel high-temperature superconductor LaFeAsO$_{0.9}$F$_{0.1}$ studied by microwave surface impedance

TL;DR

This study investigates the microwave surface impedance of LaFeAsO$_{0.9}$F$_{0.1}$, revealing a high upper critical field, significant depinning frequency, and a small penetration depth, indicating similarities to high-$T_c$ cuprate superconductors.

Contribution

The paper provides the first microwave surface impedance measurements of LaFeAsO$_{0.9}$F$_{0.1}$, highlighting its high critical field and depinning frequency, and compares its properties to cuprate superconductors.

Findings

Upper critical field approximately 56 Tesla.

Depinning frequency around 6 GHz.

Effective London penetration depth less than or equal to 200 nm.

Abstract

Temperature and magnetic field dependent measurements of the microwave surface impedance of superconducting LaFeAsO$_{0.9}$F$_{0.1}$ (\Tc $\approx$ 26K) reveal a very large upper critical field ($B_{\rm c2} \approx 56$T) and a large value of the depinning frequency ($f_{0}\approx 6$GHz); together with an upper limit for the effective London penetration depth, $\lambda_{\rm eff} \le 200 \rm nm$, our results indicate a strong similarity between this system and the high-$T_{\rm c}$ superconducting cuprates.