Electronic and phononic Raman scattering in detwinned YBa$_2$Cu$_3$O$_{6.95}$ and Y$_{0.85}$Ca$_{0.15}$Ba$_2$Cu$_3$O$_{6.95}$: s-wave admixture to the $d_{x^2-y^2}$-wave order parameter

M. Bakr, A. P. Schnyder, L. Klam +5