First-Order Type Effects in YBa${}_2$Cu${}_3$O${}_{6+x}$ at the Onset of Superconductivity

L. Tassini, W. Prestel, A. Erb +2

We present results of Raman scattering experiments on tetragonal $({\mathrm{Y}}_{1-\mathrm{y}}\mathrm{C}{\mathrm{a}}_{\mathrm{y}})\mathrm{B}{\mathrm{a}}_2\mathrm{C}{\mathrm{u}}_3{\mathrm{O}}_{6+\mathrm{x}}$ for doping levels $p(x,y)$ between 0 and 0.07 holes/CuO${}_2$. Below the o…