Discovery of robust superconductivity against volume shrinkage

The superconducting transition temperature (<i>T</i>_c) of superconductor is related intimately to multiple degree of freedom of charge, spin, orbital and lattice. Many studies have indicated that pressure is an effective way to tune <i>T</i>_c though changing crystal structure and electronic structure. Here, we report a new progress made in the high-pressure studies – discovery of a new type of superconductors whose <i>T</i>_c is robust against large volume shrinkage under extremely high pressure, named RSAVS (robust superconductivity against volume shrinkage) superconductor. Such RSAVS behavior was observed initially in the high entropy alloys of (TaNb)_0.67(HfZrTi)_0.33 and (ScZrNbTa)_0.6(RhPd)_0.4, then in the widely-used NbTi alloy, Nb and Ta elements. Analysis shows that this type of superconductor possesses a body-centered cubic crystal structure and is composed of transition metal elements. The observed results not only present new research topics but also raise the question of what determines <i>T</i>_c of conventional or unconventional superconductors.