Sub-THz electrodynamics of the graphene-like superconductor CaAlSi

TL;DR

This study investigates the sub-THz electrodynamics of CaAlSi, revealing its anisotropic superconducting gaps and optical properties, combining experimental measurements with insights into its unique crystal and electronic structure.

Contribution

First optical measurement of CaAlSi's electrodynamics, identifying multiple superconducting gaps and anisotropic optical parameters.

Findings

Detected superconducting gaps in hexagonal planes and along the c axis.

Measured anisotropic optical parameters of the normal state.

Provided the first sub-THz optical data for CaAlSi.

Abstract

We report the first optical study of CaAlSi, a superconductor which displays both the crystal structure of MgB2 and the electronic band structure of intercalated graphites. The reflectivity of a CaAlSi single crystal was measured down to sub-THz frequencies and to 3.3 K, with the use of Coherent Synchrotron Radiation. A superconducting gap in the hexagonal planes, two gaps along the c axis were found and measured, as expected from the structure of the CaAlSi Fermi surface. The anisotropic optical parameters of the normal state were also determined.