  To raise the superconducting-transition temperature (Tc) has been the driving
force for the long, sustained effort in superconductivity research. Recent
progress in hydrides with Tcs up to 287 K under 267 GPa has heralded a new era
of room-temperature superconductivity (RTS) with immense technological promise.
Indeed, RTS has lifted the temperature barrier for the ubiquitous application
of superconductivity. Unfortunately, formidable pressure is required to attain
such high Tcs. The most effective relief to this impasse is to remove the
pressure needed while retaining the pressure-induced Tc without pressure. Here
we show such a possibility in the pure and doped high-temperature
superconductor (HTS) FeSe by retaining, at ambient via pressure-quenching (PQ),
its Tc up to 37 K (quadrupling that of a pristine FeSe) and other
pressure-induced phases. We have also observed that some phases remain stable
without pressure at up to 300 K and for at least 7 days. The observations are
in qualitative agreement with our ab initio simulations using the solid-state
nudged elastic band (SSNEB) method. We strongly believe that the PQ technique
developed here can be adapted to the RTS hydrides and other materials of value
with minimal effort.
