Dresden 2017 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 70: Superconductivity: Fe-based Superconductors - Theory

TT 70.1: Hauptvortrag

Donnerstag, 23. März 2017, 15:00–15:30, HSZ 103

New Developments in the Theory of STM on Unconventional Superconductors — •Andreas Kreisel — Institut für Theoretische Physik, Uni Leipzig, Germany — Niels Bohr Institute, Copenhagen, Denmark

Scanning Tunneling Microscopy (STM) has become a widely used experimental technique to study superconductivity, yet new approaches are unraveling so far unknown properties. A number theories have been used to explain the qualitative origin of superconducting pairing in Fe-based superconductors (FeSC), but quantitative, material-specific comparisons to experimental results have been made in few cases only. Here, a novel approach to theoretical simulation of STM is outlined which combines first-principles calculations to obtain material-specific Wannier functions and lattice Green functions from BdG or T-matrix calculations. The method takes into account crystal symmetries such that it improves the traditional lattice calculations from two perspectives: Effects of the tunneling layers are contained qualitatively and the spatial resolution is not limited to the lattice spacing, thus comparable to the resolution of experimentally available data. By calculating the local density of states relevant for the tunneling process, it is possible to simulate images of impurities on the surface of superconductors. As examples, we study disorder in a cuprate superconductor and a FeSC and discuss conclusions that can be drawn about the order parameter when comparing to experimental observations.