The Thermodynamics and the Inverse Isotope Effect of superconducting PdH and PdD under pressure

TL;DR

This paper investigates the thermodynamics of superconducting PdH and PdD under pressure using Migdal-Eliashberg theory, analyzing changes in critical temperature, energy gap, and isotope effect, with results aligning well with experimental data.

Contribution

The paper introduces a general method to calculate the thermodynamics of hydrides under pressure within the Migdal-Eliashberg framework, considering a zincblende lattice structure.

Findings

Pressure affects $T_c$, specific heat jump, and energy gap.

The isotope effect coefficient varies with pressure.

Results agree well with existing experimental data.

Abstract

We present in this paper the thermodynamics of superconducting PdH and PdD under pressure. We make use of a general method to calculate the thermodynamics under pressure within the Migdal-Eliashberg theory. We have considered the crystal lattice to be zincblende taking into account the experimental evidence for both PdH and PdD at temperatures below 55 K. We have studied, in particular, the changes induced by pressure in the critical temperature, $T_c$, in the specific heat jump at $T_c$, in the energy gap at $T=0K$, in the deviation function $D(t)$ and in the isotope effect coefficient, $\alpha$. We get a very good agreement with experiment where this data exist. This method represents a basis on which the thermodynamics of other hydrides under pressure can be calculated.