Symmetry of the Superconducting Order-Parameter in Bi2sr2cacu2ox

We analyzed the symmetry of the superconducting-phase condensate of Bi2Sr2CaCu2Ox with photoemission at high energy and angular resolution. The result unambiguously demonstrates that the photohole must include non-s-wave components. Under the hypothesis of a pure d-wave symmetry, this would be identified as d(xz) + d(yz). Our superconducting state data are, specifically, incompatible with pure d(x2-y2) symmetry. Mixed symmetries, however, cannot be excluded as long as they include a non-s-wave component. We specifically observe a change in the symmetry of electronic states between the normal state and the superconducting state.