Exotic behavior of short-range coulomb interactions in non uniform charge density solids -- A Road to high temperature superconductors?
Professor George Sawatzky
University of British Columbia
Conventional theories of high temperature superconductors generally predict shortening of the Cooper pair size with increasing Tc or superconducting gap. In cuprate superconductors the coherence length is less than 1nm dor example. This however in uniform density and polarizability materials would lead to large coulomb repulsion which would kill the superconductivity. Thjis is just one of many examples in which the detailed knowledge of the short range coulomb interactions (<3nm) is essential. In materials with strong spatial (periodic) variations of the charge density and also the polarizability such as transition metal compounds including chalcogenides, halides and some pnictogens. In these cases the dielectric function is not a function of r-r’ but of r,r’ and in momentum space it is an infinite matrix. It I the effects of local field corrections and the overlap of polarization clouds of two charged particles and the consequence of interference effects that strongly change the short -ange coulomb interactions. I will describe a real space way of approximating the effects of these deviations from conventional approaches and demonstrate the result applied to the CuO2 plane of the curates resulting in strong short range minima and maxima in the effective coulomb interactions between 2 doped holes.
Hosted by Prof. Foyevtsova and Prof. Forró