The superconducting phase of the HgBa2CuO4+δ (Hg-1201) and HgBa2Ca2Cu3O8+δ (Hg-1223) cuprates has been investigated by Raman spectroscopy under hydrostatic pressure. Our analysis reveals that the increase of Tc with pressure is slower in Hg-1223 cuprate compared to the Hg-1201 due to a charge carrier concentration imbalance (accentuated by pressure) between the CuO2 layers of Hg-1223. We find that the energy variation under pressure of the apical oxygen mode from which the charge carriers are transferred to the CuO2 layers, is the same for both the Hg-1223 and Hg-1223 cuprates and it is controlled by the inter-layer compressibility. At last, we show that the binding energy of the Cooper pairs related to the maximum amplitude of the d− wave superconducting gap at the anti-nodes, does not follow Tc with pressure. It decreases while Tc increases. In the particular case of Hg-1201, the binding energy collapses from 10 to 2 KBTc as the pressure increases up to 10 GPa. These direct spectroscopic observations joined to the fact that the binding energy of the Cooper pairs at the anti-nodes does not follow Tc either with doping, raises the question of its link with the pseudogap energy scale which follows the same trend with doping.
@article{arxiv.2102.13432,
title = {Exploration of the Hg-based cuprate superconductors by Raman spectroscopy under hydrostatic pressure},
author = {N. Auvray and B. Loret and S. Chibani and R. Grasset and Y. Guarnelli and P. Parisiades and A. Forget and D. Colson and M. Cazayous and Y. Gallais and Alain Sacuto},
journal= {arXiv preprint arXiv:2102.13432},
year = {2021}
}