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Simulation of High-Resolution Scanning Tunnelling Microscopy and Spectroscopy: Present State of the Art and Comparison with Experiments Dr Werner A Hofer Surface Science Research Centre The aim of the talk is to give an overview over the current state of theoretical research in scanning tunnelling microscopy. I shall introduce the basic theoretical concept, which unifies existing models of scattering (Landauer-Buttiker approach) and perturbation (Bardeen approach) in a common framework based on non-equilibrium Green’s functions and discuss its limitations with respect to achievable currents and minimum distances [1,2]. The precision of the method is illustrated by recent simulations of oxygen covered ruthenium surfaces and detailed comparisons with experiment [3]. Interactions between STM tip and surface will be highlighted for close packed metal surfaces like gold, copper, or aluminium [4]; the method of inferring interaction energies and forces from the simulation of electron transitions, and the high elasticity of aluminum is shown to fully account for the observed giant corrugations. The second half of the talk will be devoted to recently developed
spectroscopic tools. We show that direct simulation of differential
contributions to a spectrum leads to the correct behaviour also for
demanding problems like the surface states on close packed noble metal
surfaces [5]. It is pointed out that the resolution of the simulations
accounts only for experimental data above 100K; for very low temperature
experiments new interpolation schemes need to be developed for the
bandstructure map. As a final example I shall talk about recent experiments
and simulations on ferromagnetic surfaces, where the spin-state of a single
atomic impurity can be measured and changed by STM tips. References
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