Retaining Superconducting Phases Through Low Temperature Pressure Quenching

In the past 5 years the discovery of superhydride systems with critical temperatures (T$_{c}$s) that approach and exceed room temperature has pushed the field to new heights. Unfortunately, to achieve room temperature superconductivity (RTS) requires pressures in excess of 260 GPa. One of the greatest challenges remaining in field of superconductivity (SC) is retaining RTS while lowering or removing pressure. As a potential solution, we developed a low temperature pressure quenching technique which successfully retained SC phases in Bi, and FeSe and Cu$_{x}$Fe$_{1-x}$Se. Quenching at 77 K and 4.2 K from pressures up to 23.6 GPa we retained Bi phases with varying T$_{c}$s corresponding to Bi II, III, and V. Similarly, we retained SC phases with T$_{c}$s up to 38 K in FeSe and 27 K in Cu$_{x}$Fe$_{1-x}$Se. Furthermore, the retained SC phase of Cu$_{x}$Fe$_{1-x}$Se was shown to be stable for at least 7 days when kept at 77 K. Finally, stability testing of Bi revealed a robust SC phase with T$_{c}$s corresponding to Bi-III (T$_{c}$ 7.1 K) while displaying the transient nature of other retained SC phases of Bi.