Who: Aires Ferreira, Department of Physics, University of York, United Kingdom
Place: Donostia International Physics Center
Date: Friday, 2 February 2018, 12:00
The generation of spin currents in nonmagnetic materials via electrical means has fascinated scientists since the first experimental reports of spin Hall effect (SHE) a decade ago. The SHE finds its origin in the rich charge-spin transport mechanisms triggered by spin?orbit interactions. While SHE and related non-equilibrium phenomena have been detected univocally in metals and semiconductors employing a range of experimental probes, the design of nanostructures allowing an effective electrostatic control of pure spin currents remains a big challenge.
In this talk, I will argue that skew scattering is ubiquitous in Dirac heterostructures lacking sub-lattice (C6v) symmetry. Unlike standard skew scattering in graphene , which requires spin-orbit-active or magnetic impurities, the proposed mechanism results from the tilting of Dirac eigenstates' spin texture induced by proximity effect . The tilting provides a finite out-of-plane spin polarization around each valley, allowing a sizeable SHE irrespective of the impurity type, into a remarkable analogy to the anomalous Hall effect in ferromagnetic metals. Our findings open good prospects for the all-electrical control of spin currents in van der Waals heterostructures of much current interest .
 A. Ferreira, T.G. Rappoport, M.A. Cazalilla & A.H.C. Neto."Extrinsic Spin Hall Effect Induced by Resonant Skew Scattering in Graphene" Phys. Rev. Lett. 112, 066601 (2014). C.Huang, Y.D. Chong & M.A. Cazalilla. "Direct coupling between charge current and spin polarization by extrinsic mechanisms in graphene." Phys. Rev. B 94, 085414 (2016)
 M. Offidani et al. Unpublished (2018).
 A. Avsar et al. "Spin-orbit proximity effect in graphene" Nat. Comm. 5, 4875 (2014). Z. Wang, et al., "Origin and Magnitude of 'Designer' Spin-Orbit Interaction in Graphene on Semiconducting Transition Metal Dichalcogenides". Phys. Rev. X 6, 041020 (2016). L.A. Benitez et al. "Strongly anisotropic spin relaxation in graphene-transition metal dichalcogenide heterostructures at room temperature" Nat. Phys. 10, 1038 (2017).