Optical Conductivity Evidence of Clean-Limit Superconductivity in LiFeAs

TL;DR

This study uses optical conductivity measurements to provide evidence that LiFeAs is in the clean-limit superconducting regime, showing spectral-weight loss and a penetration depth, with implications for its electronic properties.

Contribution

It presents the first optical evidence of clean-limit superconductivity in LiFeAs, linking optical properties to its superconducting state and electronic scattering mechanisms.

Findings

Spectral-weight loss indicates condensate formation in superconducting LiFeAs.

Penetration depth measured at 225 nm.

Normal state analysis suggests spin fluctuations and proximity to a quantum critical point.

Abstract

We measured the optical conductivity of superconducting LiFeAs. In the superconducting state, the formation of the condensate leads to a spectral-weight loss and yields a penetration depth of 225 nm. No sharp signature of the superconducting gap is observed. This suggests that the system is likely in the clean limit. A Drude-Lorentz parametrization of the data in the normal state reveals a quasiparticle scattering rate supportive of spin fluctuations and proximity to a quantum critical point.