Dresden 2009 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 13: Electronic structure II
O 13.6: Vortrag
Montag, 23. März 2009, 16:15–16:30, SCH A216
Symmetry Analysis of Tunnel Current Eigenchannels — •Martyna Polok1, Dmitry Fedorov1, Steven Walczak1,2, Peter Zahn1, and Ingrid Mertig1,2 — 1Martin-Luther-Universität Halle, Institut für Physik, D-06099 Halle, Germany — 2Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, D-06120 Halle, Germany
Thanks to advances in Scanning Tunneling Microscopy (STM) it is now possible to probe both the electronic and magnetic properties of surfaces. We present an ab initio study of a tip approaching a Cu(001) surface decorated with a single Cu or Co adatom.
Electronic transport is calculated using the Kubo linear response theory in the Baranger and Stone formalism. This description is equivalent to the Landauer language, where conductance is understood as a sum over all transmission eigenchannels.
For a magnetic system additional channels created by the 3d electrons can cause an increase in the tunnel current. The transmission amplitude of the eigenchannels depends on the overlap between those valence orbitals available at the Fermi energy εF. A detailed study of the local density of states shows that in the case of magnetic adatoms this is a spin dependent effect. For the investigated systems the majority spin current is dominated by electrons with spherically symmetric orbitals in the plane perpendicular to the transport direction (z), these are the s, pz, and dz2 orbitals. For the minority spin channel electrons with asymmetric orbitals, px, py, dxz, and dyz, dominate at the Fermi energy and therefore determine the current distribution.