Studies of superconductivity and structure for CaC6 to pressures above 15 GPa

TL;DR

This study investigates how the superconducting transition temperature of CaC6 changes under high pressure, revealing an initial increase followed by a sharp drop and a structural phase transition around 10 GPa.

Contribution

It provides detailed measurements of Tc under pressure and identifies a structural transition in CaC6 at high pressures.

Findings

Tc increases at +0.39 K/GPa up to 10 GPa

Tc drops abruptly from 15 K to 4 K at 10 GPa

Structural transition from rhombohedral to higher symmetry phase near 10 GPa

Abstract

The dependence of the superconducting transition temperature Tc of CaC6 has been determined as a function of hydrostatic pressure in both helium-loaded gas and diamond-anvil cells to 0.6 and 32 GPa, respectively. Following an initial increase at the rate +0.39(1) K/GPa, Tc drops abruptly from 15 K to 4 K at 10 GPa. Synchrotron x-ray measurements to 15 GPa point to a structural transition near 10 GPa from a rhombohedral to a higher symmetry phase.