Pressure Evolution of Superconducting T_c in High Entropy Alloys from First-Principles Investigation

High Entropy Alloy (HEA) superconductors show promise for extreme-environment applications due to the stability and unexplained robust superconductivity gained from their disordered structures. One of the most widely used superconductors in medical imaging and superconducting magnets is NbTi, an alloy which has a high critical field strength, H_c2, but has a low T_c and even lower T_c under pressure. Many HEAs, including those with Nb-Ti components, were found to exhibit higher T_c while maintaining high H_c2 under pressure. A natural question one might ask is where the robust superconducting properties of HEA superconductors originate. Here, we will present first-principles investigation into HEA superconductors from the perspective of the pressure evolution of their electronic structure, phonon spectra, electron-phonon coupling strength, and superconducting T_c based on the Migdal-Eliashberg theory. The simulation results for Nb metal, NbTi alloy, and NbTi HEA will be presented and discussed.