Exploration of Hg-based cuprate superconductors by Raman spectroscopy under hydrostatic pressure

The superconducting phase of the ${\mathrm{HgBa}}_{2}{\mathrm{CuO}}_{4+\ensuremath{\delta}}$ (Hg-1201) and ${\mathrm{HgBa}}_{2}{\mathrm{Ca}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{8+\ensuremath{\delta}}$ (Hg-1223) cuprates has been investigated by Raman spectroscopy under hydrostatic pressure. Our analysis reveals that increase ${T}_{\mathrm{c}}\phantom{\rule{0.16em}{0ex}}$with pressure is slower in Hg-1223 cuprate compared to Hg-1201 due a charge carrier concentration imbalance accentuated Hg-1223. We find energy variation apical oxygen mode from which carriers are transferred ${\mathrm{CuO}}_{2}$ layer, same for both it controlled interlayer compressibility. At last, we show binding Cooper pairs related maximum amplitude $d$-wave gap at antinodes does not follow It decreases while ${T}_{\mathrm{c}}\phantom{\rule{0.16em}{0ex}}$increases. In particular case Hg-1201, collapses 10 2 ${K}_{B}{T}_{\mathrm{c}}\phantom{\rule{0.16em}{0ex}}$ as increases up GPa. These direct spectroscopic observations joined fact ${T}_{\mathrm{c}}\phantom{\rule{0.16em}{0ex}}$either with doping, raises question its link pseudogap scale follows trend doping.