The Never-Ending Frontier of Advancing T_c: A Third Way to A New Height of 151 K in HBCCO at Ambient without Pressure

The search for higher T_c has provided the essential impetus for the continuous interest and effort in superconductivity science and technology research for more than a century, ever since its discovery by Kamerlingh Onnes. Great progress has been made. Unfortunately, all record high T_cs in different compound systems are achieved only under high pressures, e.g. 164 K in stable cuprate HBCCO under 31 GPa^a and 260 K in unstable hydride LaH10 under 180-200 GPa^b. The high pressure required to achieve these high T_cs has impeded the development of superconductivity science and applications. Recently, we have succeeded in providing relief to this impasse by achieving a record high T_c of 151 K in HBCCO at ambient without pressure via the pressure-quench protocol (PQP) developed by us. In this talk, I shall present our experimental results and discuss the rationale for, and the execution and potential implications of, PQP in the development of high-temperature superconductors and of compounds with significant properties other than superconductivity in their metastable states.

^a L. Gao et al., PRB 50, 4260(R) (1994)

^b M. Somayazulu et al., PRL 122, 027001 (2019)