Quasiparticle interference from magnetic impurities

Abstract: Fourier transform scanning tunneling spectroscopy (FT-STS) measures the scattering of conduction electrons from impurities and defects, giving information about the electronic structure of both the host material and adsorbed impurities. We interpret such FT-STS measurements in terms of the quasiparticle interference (QPI), investigating the QPI due to magnetic impurities adsorbed on a range of representative non-magnetic host surfaces, and contrasting with the case of a simple scalar impurity or point defect. We demonstrate how the electronic correlations present for magnetic impurities markedly affect the QPI, showing e.g. a large intensity enhancement due to the Kondo effect, and universality at low temperatures/scanning-energies. The commonly-used joint density of states (JDOS) interpretation of FT-STS measurements is also considered, and shown to be insuffcient in many cases, including that of magnetic impurities.