RSAVS superconductors: materials with a superconducting state that is robust against large volume shrinkage

TL;DR

This paper introduces a new class of superconductors called RSAVS that maintain a nearly constant transition temperature despite large volume shrinkages caused by high pressure, revealing a universal behavior in some conventional superconductors.

Contribution

The study identifies and characterizes RSAVS superconductors, demonstrating their pressure-robust transition temperature and providing electronic structure insights into their stability.

Findings

TC remains almost constant over large pressure ranges (up to 141 GPa).

RSAVS behavior is observed in multiple alloys and elemental superconductors.

Electronic structure calculations suggest specific orbitals stabilize TC under pressure.

Abstract

TThe transition temperature (TC) between normal and superconducting states usually exhibits a dramatic increase or decrease with increasing applied pressure. Here we present, in contrast, a new kind of superconductor that exhibits the exotic feature that TC is robust against large volume shrinkages induced by applied pressure (here naming them as "RSAVS superconductors"). Extraordinarily, the TC in these materials stays almost constant over a large pressure range, e.g. over 136 GPa in the (TaNb)0.67(HfZrTi)0.33 high entropy alloy and 141 GPa in the NbTi commercial alloy. We show that the RSAVS behavior also exists in another high entropy alloy (ScZrNbTa)0.6(RhPd)0.4, and in superconducting elemental Ta and Nb, indicating that this behavior, which has never previously been identified or predicted by theory, occurs universally in some conventional superconductors. Our electronic structure calculations indicate that although the electronic density of state (DOS) at the Fermi level in the RSAVS state is dominated by the electrons from the degenerate dxy, dxz and dyz orbitals, these electrons decrease in influence with increasing pressure. In contrast, however, the contribution of the degenerate dx2-y2 and dz2 orbital electrons remains almost unchanged at the Fermi level, suggesting that these are the electrons that may play a crucial role in stabilizing the TC in the RSAVS state.