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B07 - Momentum-resolved dynamics of relaxation processes and control of spins and pseudospins in two-dimensional spintronic heterostructures

A range of semiconducting transition metal dichalcogenides (TMDCs) exhibits a unique electronic structure governed by spin-polarized electronic states localized both in momentum and real space. These materials open new perspectives in view of spintronic applications, for instance as source of spin currents in heterostructures. For example, spin- and valley-selective excitation localized in a TMDC layer can be induced by circular polarized light leading to ultrafast scattering processes in momentum space followed by charge and spin transfer to adjacent layers via electronic states which are delocalized across a heterostructure interface. This project employs femtosecond time-, energy- and momentum-resolved XUV photoemission spectroscopy (trARPES) to probe spin-, valley- and layer-dependent electronic excitations, ultrafast excited state carrier scattering and spin transfer processes in TMDCs and TMDC-based heterostructures with ferro- and paramagnetic metals. These processes will be initiated by ultrashort optical laser pulses with selected (linear/circular) polarization. Our goal is obtaining a microscopic understanding of excited state scattering dynamics, relaxation phenomena and spin-transfer processes across various heterostructure interfaces. Furthermore, we will study the dependence of the dynamics on external parameters like strain, electric fields, and interfacial coupling in TMDC-metal heterostructures. These studies will be performed in close collaboration with the projects B08 (Bolotin / Gahl) and B09 (Marques). The long-term goal of our work is to elucidate the potential of TMDCs for ultrafast spintronics and to reveal the underlying fundamental processes of spin- and charge transfer and energy dissipation.

Publications (1st Funding Period 2018 - 2021)