Evidence for superconductivity at 190 K in a pressure-overdoped cuprate
It is well established that the critical temperature ($T_c$) of cuprate superconductors can be tuned by pressure. For example, compression decouples the hole doping from chemical doping allowing for overdoped samples far beyond what is possible at ambient pressure. In this work, multiple techniques are used to probe the onset of the Meissner effect at $T_c$ as a function of pressure in $\mathrm{Pb_{0.4}Bi_{1.6}Sr_2Ca_2Cu_3O_{10+δ}}$ (Bi-2223) to 60 GPa in different compression environments. Samples compressed under quasihydrostatic conditions exhibit a distinctive non-monotonic pressure dependence of $T_c$ below 25 GPa, in agreement with previous reports. With further increase in pressure $T_c$ climbs continuously to 190 K at 60 GPa. Evidence for critical temperatures exceeding those reported to date for cuprates at ambient and high pressures, the results may be understood in terms of the proposed second superconducting regime at high hole doping.