Quasi-2D superconductivity and Fermi-liquid behavior in bulk CaC$_6$

TL;DR

This study investigates the superconducting and normal-state properties of bulk CaC6, revealing quasi-2D superconductivity, Fermi-liquid behavior above Tc, and intermediate electron-phonon coupling, consistent with BCS theory.

Contribution

It provides comprehensive experimental evidence of quasi-2D superconductivity and Fermi-liquid behavior in bulk CaC6, with detailed analysis of electron-phonon interactions.

Findings

Resistivity follows T^2 dependence up to 50 K, indicating Fermi-liquid behavior.

Upper critical field measurements suggest quasi-2D superconductivity.

Electron-phonon coupling constant estimated at 0.85, indicating intermediate coupling.

Abstract

The intercalated graphite superconductor CaC6 with Tc ~ 11.5 K has been synthesized and characterized with magnetoresistance measurements. Above the transition, the resistivity follows a T^2 dependence up to 50 K, which suggests Fermi liquid behavior. Above 50 K, the data can be fit to the Bloch-Gruneisen model providing a Debye temperature of theta = 263 K. By using McMillan formula, we estimate the electron-phonon coupling constant of lambda = 0.85 which places this material in the intermediate-coupling regime. The upper critical field is determined parallel and perpendicular to the superconducting planes, and the dependence of the upper critical field as a function of angle suggests that this is a quasi-2D superconductivity. All of these measurements are consistent with BCS-like superconductivity.