Unraveling the Robust Superconductivity Phenomenon of High-Entropy Alloy

TL;DR

This study investigates the persistent superconductivity in niobium-based high-entropy alloys under extreme pressure, revealing a compensation mechanism that maintains the critical temperature and aligns well with experimental data.

Contribution

It provides a first-principles explanation for the robustness of superconductivity in high-entropy alloys under high pressure, highlighting the role of electronic and phonon property compensation.

Findings

Superconductivity remains stable up to 100 GPa in studied alloys.

Electronic and phonon properties compensate under pressure.

First-principles $T_c$ calculations match experimental results.

Abstract

Recent experiments demonstrate a "robust superconductivity phenomenon" in niobium-based alloys, where the superconducting state remains intact and the critical temperature ($T_c$) is largely unaffected by external pressure well above tens of gigapascal (GPa) into the megabar regime ($\ge 100 GPa$). Motivated by these observations, we perform first-principles electron-phonon calculations for body-centered cubic Nb and NbTi crystals, as well as for special quasi-random structures of Nb$_{0.5}$Ti$_{0.5}$ and (NbTa)$_{0.7}$(HfZrTi)$_{0.3}$ high-entropy alloy (HEA). The calculations unravel the underlying mechanism of robust superconductivity, stemming from a compensation effect between varying electronic and phonon properties under pressure. The results also reveal how structural and chemical disorders modify the superconducting state. The first-principles $T_c$ values agree quantitatively with the experiments throughout the entire pressure range under study. Our work thereby paves the way for exploring superconducting HEAs under pressure via advanced first-principles simulations.