Pressure effects on the superconductivity of HfPd2Al Heusler compound: Experimental and theoretical study

TL;DR

This study investigates how applying pressure affects the superconducting properties of HfPd2Al, combining experimental high-pressure x-ray diffraction and resistivity measurements with first-principles calculations to understand the decrease in critical temperature.

Contribution

It provides a combined experimental and theoretical analysis of pressure effects on HfPd2Al's superconductivity, revealing the relationship between lattice stiffening and Tc reduction.

Findings

Superconducting critical temperature decreases linearly with pressure.

Electron-phonon coupling constant diminishes as pressure increases.

Theoretical calculations support experimental observation of Tc decrease due to lattice stiffening.

Abstract

Polycrystalline HfPd2Al has been synthesized using the arc-melting method and studied under ambient pressure conditions by x-ray diffraction from room temperature up to 450^oC. High pressure x-ray diffraction up to 23 GPa was also performed using Diacell-type membrane diamond anvil cells. The estimated linear thermal expansion coefficient was found to be {\alpha} = 1.40(3)x10^{-5} K^{-1}, and the bulk modulus derived from the fit to the 3rd order Birch-Murnaghan EOS (BMEOS) is B0 = 97(2) GPa. Resistivity studies under applied pressure (p < 7.49 GPa) showed a linear decrease of superconducting critical temperature with increasing pressure and the slope dTc/dp = -0.13(1) K GPa^{-1}. The same behavior is observed for the electron-phonon coupling constant {\lambda_{ep}}(p) that changes from 0.67 to 0.6, estimated for p = 0.05 GPa and 7.49 GPa, respectively. First principles electronic structure and phonon calculation results are presented and used to estimate the magnitude of electron-phonon interaction {\lambda_{ep}} and its evolution with pressure. Theoretical results explain the experimentally observed decrease in Tc due to considerable lattice stiffening.