Atomic-scale quasi-particle scattering resonances in Bi2Sr2CaCu2O8+delta

Low-temperature scanning tunneling spectroscopy of the high transition temp erature (high-T-c) cuprate Bi2Sr2CaCu2O8+delta reveals the existence of lar ge numbers of identical regions with diameters of about 3 nanometers that h ave a relatively high density of low-energy quasi-particle states. Their sp atial and spectroscopic characteristics are consistent with theories of str ong quasi-particle scattering from atomic-scale impurities in a d-wave supe rconductor. These characteristics include breaking of local particle-hole s ymmetry, a diameter near twice the superconducting coherence length, and an inverse square dependence of their local density-of-states on distance fro m the scattering center. In addition to the validation of d-wave quasi-part icle scattering theories, these observations identify a source for the anom alously high levels of low-energy quasi-particles in Bi2Sr2CaCu2O8+delta at low temperatures.