Retaining Superconducting Phases Through Low-Temperature Pressure Quenching

In the past seven years impressively high superconducting critical temperatures (T_cs) have been reported in numerous superhydride systems. Among these include T_cs which approach room temperature (RT) but require pressure exceeding 150 GPa. Retaining these enhanced T_cs while lowering or removing the applied pressure remains a significant challenge in the field. We have therefore employed a low-temperature pressure-quenching (PQing) technique to retain high-pressure induced superconducting phases in single-crystal Bi. PQing at 77 K and 4.2 K from pressures up to 26.6 GPa, we retained Bi phases with varying T_cs corresponding to Bi-II, Bi-III and Bi-V, as well as several unidentified superconducting phases. Stability testing of the retained phases at 4.2 K revealed good phase stability over time for T < 20 K. PQing displayed further utility by providing evidence for the transition of Bi-I to Bi-III via a superconducting amorphous phase and revealing a new record T_c of 9.05 K in Bi when PQed at 26.5 GPa and 4.2 K.