Optical Study of LaO_0.9F_0.1FeAs: Evidence for a Weakly Coupled Superconducting State

TL;DR

This study investigates the optical properties of LaO_0.9F_0.1FeAs, revealing evidence for a weakly coupled superconducting state through infrared reflectance measurements and analysis of phonons, plasma edge, and interband transitions.

Contribution

It provides the first optical characterization of LaO_0.9F_0.1FeAs, estimating a low electron-boson coupling constant indicating weak coupling superconductivity.

Findings

Observation of infrared active phonons and plasma edge.

Estimated electron-boson coupling constant ~ 0.6.

Evidence supporting a weakly coupled superconducting state.

Abstract

We have studied the reflectance of the recently discovered superconductor LaO_0.9F0.FeAs in a wide energy range from the far infrared to the visible regime. We report on the observation of infrared active phonons, the plasma edge (PE) and possible interband transitions. On the basis of this data and the reported in-plane penetration depth lambda_L(0) about 254 nm [H. Luetkens et al., Phys. Rev. Lett. v. 101, 0970009 (2008)] a disorder sensitive relatively small value of the total electron electron-boson coupling constant lambda_tot=lambda_e-ph+lambda_e-sp ~ 0.6 +- 0.35 can be estimated adopting an effective single-band picture.