$\left({\mathrm{Cu}}_{0.5}{\mathrm{C}}_{0.5}\right){\mathrm{Ba}}_2{\mathrm{Ca}}_{m-1}{\mathrm{Cu}}_m{\mathrm{O}}_x$ for $m=3\mathrm{}$ and 4 under hydrostatic pressure

The hydrostatic pressure effects on the superconducting transition temperatures ${(T}_c\mathrm{’}\mathrm{s})$ of the oxycarbonate cuprates $\left({\mathrm{Cu}}_{0.5}{\mathrm{C}}_{0.5}\right){\mathrm{Ba}}_2{\mathrm{Ca}}_{m-1}{\mathrm{Cu}}_m{\mathrm{O}}_x\hspace{0.5em}\left[\right(\mathrm{C}\mathrm{u},\mathrm{C})-12(m-1\left)m\right],$ have been determined for $m=3\mathrm{}$ and 4 with different dopings of $x$’s. We found that, similar to ${\mathrm{YBa}}_2{\mathrm{Cu}}_3{\mathrm{O}}_x,\hspace{0.5em}{\mathrm{dT}}_c/dP$ depends strongly on x for (Cu,C)-1223 and increases from $-0.7$ to $+1.2\mathrm{}\hspace{0.5em}\mathrm{K}/\mathrm{GPa}$ as x decreases and the compound changes from overdoped to nearly optimally doped, consistent with the prediction of the phenomenological model on the pressure effect on $T_c.$ In contrast to the prediction, ${\mathrm{dT}}_c/dP$ depends only slightly on x for (Cu,C)-1234 and decreases from $0.75$ to $0.6\hspace{0.5em}\mathrm{K}/\mathrm{GPa}$ as x decreases from nearly optimally doped to underdoped. The ${\mathrm{dT}}_c/dP$ difference is attributed to the possible different electronic contribution of the CuO chains in the two compounds, as implied by the distinct temperature dependences of their thermoelectric power.