Regensburg 2022 – scientific programme

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O: Fachverband Oberflächenphysik

O 2: Ultrafast Electron Dynamics at Surfaces and Interfaces 1

O 2.3: Talk

Monday, September 5, 2022, 11:00–11:15, H3

Anisotropic carrier dynamics in a laser-excited Fe/(MgO)(001) heterostructure from real-time TDDFT — •Elaheh Shomali, Markus Ernst Gruner, and Rossitza Pentcheva — Department of Physics and Center for Nanointegration, CENIDE, University of Duisburg-Essen, Germany

The interaction of a femtosecond optical pulse with a Fe_n/(MgO)_m(001) (n=1,3,5 and m=3,5,7) metal/oxide heterostructure is addressed using time-dependent density functional theory (TDDFT) calculations in the real-time domain. We systematically study electronic excitations as a function of laser frequency (around and higher than the bulk MgO band gap). We find a marked anisotropy in the response to in- and out-of-plane polarized light, which changes its character qualitatively depending on the excitation energy: the Fe-layer is efficiently addressed at low frequencies by in-plane polarized light, whereas for frequencies higher than the MgO band gap, we find a particularly large sensitivity of MgO-layers to cross-plane polarized light. Moreover, the interface plays an important role, as it mediates transitions from the valence band of MgO into the 3d states of Fe closely above the Fermi-level and transitions from the Fe-states below the Fermi level into the conduction band of MgO. As these transitions can occur simultaneously without altering the charge balance of the layers, they could potentially lead to an efficient transfer of excited carriers into the MgO part [1]. Funding by SFB 1242, project C02, is gratefully acknowledged. [1] E. Shomali, M. E. Gruner, R. Pentcheva, Phys. Rev. B, in press, arXiv:2205.03178.