Regensburg 2016 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 4: Surface Magnetism: Atoms and Molecules

O 4.5: Vortrag

Montag, 7. März 2016, 11:30–11:45, S052

Theory of Inelastic Electron Tunneling through an Adatom: Perturbation Expansion around the Atomic Limit — •Jindrich Kolorenc — Institute of Physics, Czech Academy of Sciences, Prague, Czech Republic

We investigate tunneling of electrons from an STM tip to a substrate through a magnetic adatom. We assume weak coupling between the tip and the adatom as well as between the adatom and the substrate, and we include these couplings only in the lowest order of the perturbation theory. We employ the Kramers–Heisenberg formula to evaluate the probabilities of coherent two-step processes that contribute to the tunneling current (for instance, an electron tunnels from the tip to the adatom and then continues from the adatom to the substrate). Our method is closely related to the cotunneling theory of Ref. [1], but it appears somewhat more straightforward and allows us to derive a relatively compact formula for the differential conductance. The steps appearing in the differential-conductance spectra are identified with excitations in the magnetic adatom that can be parametrized on the basis of first-principles calculations without resorting to an effective spin model. The method is straightforwardly applicable to cases with strong spin-orbital coupling (f electrons) where the spin is not a good quantum number.

[1] F. Delgado and J. Fernández-Rossier, Phys. Rev. B 84, 045439 (2011)