Pressure effects on the electronic structure and superconductivity of (TaNb)0.67(HfZrTi)0.33 high entropy alloy

Effects of pressure on the electronic structure, electron-phonon interaction, and superconductivity of the high entropy alloy ${(\mathrm{TaNb})}_{0.67}{(\mathrm{HfZrTi})}_{0.33}$ are studied in the pressure range 0--100 GPa. The electronic structure is calculated using the Korringa-Kohn-Rostoker method with the coherent potential approximation. Effects of pressure on the lattice dynamics are simulated using the Debye-Gr\"uneisen model and the Gr\"uneisen parameter at ambient conditions. In addition, the Debye temperature and Sommerfeld electronic heat capacity coefficient were experimentally determined. The electron-phonon coupling parameter $\ensuremath{\lambda}$ is calculated using the McMillan-Hopfield parameters and computed within the rigid muffin-tin approximation. We find that the system undergoes the Lifshitz transition, as one of the bands crosses the Fermi level at elevated pressures. The electron-phonon coupling parameter $\ensuremath{\lambda}$ decreases above 10 GPa. The calculated superconducting ${T}_{c}$ increases up to 40--50 GPa and, later, is stabilized at the larger value than for the ambient conditions, in agreement with the experimental findings. Our results show that the experimentally observed evolution of ${T}_{c}$ with pressure in ${(\mathrm{TaNb})}_{0.67}{(\mathrm{HfZrTi})}_{0.33}$ can be well explained by the classical electron-phonon mechanism.