Modification of structural disorder by hydrostatic-pressure in superconducting YBa${}_2$Cu${}_3$O${}_{6.73}$ cuprate

Abstract

Compelling efforts to improve the critical temperature ($T_c$) of superconductors have been made through high-pressure application. Understanding the underlying mechanism behind such improvements is critically important, however, much remains unclear. Here we studied ortho-III YBa${}_2$Cu${}_3$O${}_{6.73}$ (YBCO) using x-ray scattering under hydrostatic-pressure (HP) up to ~6.0 GPa. We found the reinforced oxygen order (OO) of YBCO under HP, revealing an oxygen rearrangement in the Cu-O layer, which evidently shows the charge transfer phenomenon between the CuO${}_2$ plane and Cu-O layer. Concurrently, we also observed no disorder-pinned charge density wave (CDW) signature in CuO${}_2$ plane under HP. This indicates that the oxygen rearrangement modifies the quenched disorder state in the CuO${}_2$ plane. Using these results, we appropriately explain why pressure-condition can achieve higher $T_c$ compared with the optimal $T_c$ under ambient pressure in YBa${}_2$Cu${}_3$O${}_{6+x}$. As an implication of these results, finally, we have discussed that the change in disorder could make it easier for YBa${}_2$Cu${}_3$O${}_{6+x}$ to undergo a transition to the nematic order under an external magnetic field.

24 pages, 6 figures