Regensburg 2019 – scientific programme

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O: Fachverband Oberflächenphysik

O 97: Ultrafast Electron Dynamics at Surfaces and Interfaces III

O 97.9: Talk

Friday, April 5, 2019, 12:30–12:45, H16

Dynamics of optical excitations in a Fe/MgO(001) heterostructure from time-dependent density functional theory — •Markus Ernst Gruner, Elaheh Shomali, and Rossitza Pentcheva — Faculty of Physics and Center for Nanointegration, CENIDE, University of Duisburg-Essen, Germany

In the framework of real-time time-dependent density functional theory (RT-TDDFT) we unravel the layer-resolved dynamics of the electronic structure of a (Fe)₁/(MgO)₃(001) multilayer system after an optical excitation with a frequency below the band gap of bulk MgO. Substantial transient changes to the electronic structure, which persist after the duration of the pulse, are observed in particular for in-plane polarized electric fields, corresponding to a laser pulse arriving perpendicular to the interface. While the strongest charge redistribution takes place in the Fe layer, a time-dependent change in the occupation numbers is visible in all layers, mediated by the presence of interface states. The time evolution of the layer-resolved occupation numbers indicates a strong orbital dependence with the depletion from in-plane orbitals (e.g. d_x²−y² of Fe) and accumulation in out-of-plane orbitals (d_z² of Fe and p_z of apical oxygen). We also see a small net charge transfer away from oxygen towards the Mg sites even for MgO layers, which are not directly in contact with the metallic Fe.
Financial support from the DFG within SFB 1242 (project C02) is gratefully acknowledged.