SKM 2023 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 8: Ultrafast Electron Dynamics at Surface and Interfaces I

O 8.2: Vortrag

Montag, 27. März 2023, 10:45–11:00, TRE Phy

Impact of layer thickness on the anisotropic carrier dynamics of a laser-excited Fe_n/(MgO)_m(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 carrier dynamics of Fe_n/(MgO)_m(001) metal/insulator heterostructures has been investigated from first-principles as a function of the Fe and MgO layer thickness (n=1,3,5 and m=3,5,7), excitation energy and polarization direction. The imaginary part of the dielectric tensor calculated within the random phase approximation (RPA) shows for all structures a similar metallic-like behavior in the in-plane component, є_xx(ω), whereas for є_zz(ω) the initially low response below the MgO band gap for Fe₁/(MgO)₃(001) increases substantially with the number of Fe layers. Electronic excitations calculated in the framework of RT-TDDFT confirm the concerted excitation mechanism previously proposed for Fe₁/(MgO)₃(001) also for the larger systems, which involves two simultaneous excitations via interface states [1]: one from occupied states of the metal to the conduction band of the insulator and simultaneously, another from the valence band of MgO into Fe states above the Fermi level. This mechanism allows for an effective bidirectional relocation of excitations between the metallic and insulating subsystems even for photon energies below the MgO gap. Funding by DFG via SFB 1242, project C02 is gratefully acknowledged. [1] E. Shomali, M. E. Gruner, and R. Pentcheva, Phys. Rev. B 105, 245103 (2022).