Influence of Pressure on the Structure and Electronic Properties of the Layered Superconductor Y2C2I2

TL;DR

This study investigates how hydrostatic pressure affects the structure and electronic properties of the layered superconductor Y2C2I2, revealing anisotropic compressibility and pressure-induced enhancements in electronic density of states that influence its superconducting transition temperature.

Contribution

It provides new insights into the pressure dependence of structural and electronic properties of Y2C2I2 using neutron diffraction and electronic structure calculations.

Findings

Compressibility is anisotropic, with perpendicular compressibility twice that within layers.

Electronic density of states at the Fermi level increases with pressure.

Superconducting transition temperature Tc increases and saturates near 2 GPa.

Abstract

The structural properties under hydrostatic pressure up to 3 GPa of the layered rare earth carbide halide superconductor Y2C2I2 are studied by neutron powder diffraction at room temperature. The compressibilities are anisotropic, such that the compressibility perpendicular to the layers being approximately twice as large as within the layers. The atomic positional parameters determined from the powder diffraction patterns as a function of pressure were used as the basis for highly resolved electronic structure calculations. These reveal the electronic density of states at E_F to increase with pressure. As is shown quantitatively, this effect outweighs the pressure induced lattice stiffening effects and is responsible for the pressure induced increase and saturation of Tc towards 2 GPa.