Superconductivity up to 164 K in ${\mathrm{HgBa}}_2$${\mathrm{Ca}}_{\mathit{m}\mathrm{-}1}$${\mathrm{Cu}}_{\mathit{m}}$${\mathrm{O}}_{2\mathit{m}+2+\mathrm{\delta }}$ (m=1, 2, and 3) under quasihydrostatic pressures

The superconducting transition temperatures (${\mathit{T}}_{\mathit{c}}$’s) of optimally doped ${\mathrm{HgBa}}_2$${\mathrm{Ca}}_{\mathit{m}\mathrm{-}1}$${\mathrm{Cu}}_{\mathit{m}}$${\mathrm{O}}_{2\mathit{m}+2+\mathrm{\delta }}$ (Hg 1:2:m-1:m) with m=1, 2, and 3 and ${\mathrm{Hg}}_{1\mathrm{-}\mathit{x}}$${\mathrm{Pb}}_{\mathit{x}}$${\mathrm{Ba}}_2$${\mathrm{Ca}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_{8+\mathrm{\delta }}$ [Hg(xPb) 1:2:2:3] have been investigated resistively under quasihydrostatic pressures up to 45 GPa. There seems to be a universal upward shift of ${\mathit{T}}_{\mathit{c}}$ under pressure, regardless of m, for all Hg 1:2:m-1:m, implying a common origin for all compounds. Record high ${\mathit{T}}_{\mathit{c}}$’s of 164, 154, and 118 K were reached for the optimally doped Hg 1:2:m-1:m with m=3, 2, and 1, respectively. However, the ${\mathit{T}}_{\mathit{c}}$ enhancement is suppressed by Pb substitution, suggesting the possibility that Hg plays an important role in these compounds.