Berlin 2018 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 50: HL Poster IV

HL 50.17: Poster

Thursday, March 15, 2018, 19:00–21:00, Poster B

Simulation of Spin Transport with Spatially Varying Transport Parameters — •Daniel Schiermeier, Stefan Hartl, Tobias Völkl, Dieter Weiss, and Jonathan Eroms — Institute of Experimental and Applied Physics, University of Regensburg, Regensburg, Germany

Spin transport properties of graphene devices are typically determined from Hanle spin precession measurements by using an analytical solution of the Bloch equation, which assumes infinitely long transport channels and uniform parameters. We investigate the influence of spatially varying parameters on the measured Hanle curves by finite element simulations using Comsol Multiphysics. To this end, we developed a model considering electric currents and spin transport properties, e.g., spin lifetime anisotropy. Thus we are able to simulate spin transport in suspended graphene, to investigate background signals originating from Hall effect due to pinholes within tunnel barriers and to explore the influence of a finite flake size and non-magnetic reference electrodes. We demonstrate that in case of uniform spin transport parameters one can overestimate the extracted spin lifetimes from Hanle measurements. In contrast, if one graphene region in a non-local spin valve device exhibits a comparatively short spin lifetime, by, e.g., contact-induced spin dephasing or lower mobility graphene parts directly connected to a suspended region, this will also affect the spin lifetime extracted in any other region, which becomes underestimated. Furthermore, we simulate normal and inverse spin Hall effect in WSe₂ graphene heterostructures to optimize our sample fabrication.