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

Abstract

The 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 type of superconductor that exhibits the exotic feature that 𝑇C is robust against large volume shrinkages (RSAVS, so naming them “RSAVS superconductors”) induced by applied pressure. Extraordinarily, our previous studies found that the 𝑇C in the two 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. Here, 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 occurs universally in a certain kind of superconductor, composed of only transition metal elements, with a body-centered cubic lattice. Our electronic structure calculations indicate that in the RSAVS state 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. We preliminarily analyzed the reasonability and validity of this suggestion by the Homes law.