Quasiparticle Scattering at Individual Impurity Atoms in High Temperature Superconductors

Materials displaying high temperature superconductivity are important for a wide range of devices as well as for physics fundamentals. Within this context, impurity atoms play an important role. It is well known that many applications depend crucially on the type and the concentration of such impurity atoms (such as Ni and Zn). There are, however, only very few investigations dealing with this issue on the microscopic level. Recently, J. C. Davis and co-workers at the University of California in Berkeley succeeded to investigate the local electronic states of the impurity atoms (quasiparticle scattering) in a high temperature superconductor by means of a specially designed scanning tunnelling microscope. The new project will investigate the universality of these effects with respect to the type of the high temperature superconductor and the impurity atoms. In addition, the effect of temperature is studied (thermal quasiparticles). On the one hand the new results will be of importance for devices which depend on the type and concentration of impurity atoms. On the other hand, however, the results will also be important for the fundamentals of the physics of high temperature superconductivity. This ranges from the understanding of quasiparticle scattering on the microscopic level to the testing of the theories describing the mechanisms of high temperature superductivity.