Robust d x 2 − y 2 Pairing Symmetry in Hole-Doped Cuprate Superconductors

摘要: Although initially quite controversial, it is now widely accepted that the Cooper pairs in optimally doped cuprate superconductors have predominantly ${d}_{{x}^{2}\ensuremath{-}{y}^{2}}$ wave function symmetry, and controversy has shifted to whether pairing symmetry changes away from optimal doping. Here we present phase-sensitive tricrystal experiments on three systems: ${\mathrm{Y}}_{0.7}{\mathrm{C}\mathrm{a}}_{0.3}{\mathrm{B}\mathrm{a}}_{2}{\mathrm{C}\mathrm{u}}_{3}{\mathrm{O}}_{7\ensuremath{-}\ensuremath{\delta}}$ (Ca-doped Y-123), ${\mathrm{L}\mathrm{a}}_{2\ensuremath{-}x}{\mathrm{S}\mathrm{r}}_{x}{\mathrm{C}\mathrm{u}\mathrm{O}}_{4}$ (La-214), ${\mathrm{B}\mathrm{i}}_{2}{\mathrm{S}\mathrm{r}}_{2}{\mathrm{C}\mathrm{a}\mathrm{C}\mathrm{u}}_{2}{\mathrm{O}}_{8+\ensuremath{\delta}}$ (Bi-2212), with doping levels covering underdoped, optimal, overdoped regions. Our work implies robust over a large variation