Proximity-induced skew scattering: a new mechanism for spin Hall effect (CANCELLED!)

DIPC Seminars

Speaker: Aires Ferreira, Department of Physics, University of York, United Kingdom
When: 2018/02/02
13:00
Place: Donostia International Physics Center
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Proximity-induced skew scattering: a new mechanism for spin Hall effect (CANCELLED!)

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 [1], which requires spin-orbit-active or magnetic impurities, the proposed mechanism results from the tilting of Dirac eigenstates' spin texture induced by proximity effect [2]. 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 [3]. [1] 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) [2] M. Offidani et al. Unpublished (2018). [3] 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).