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Special CAMP Symposium: Spins in Graphene: All-Electric Spintronics in Graphene

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Aires Ferreira, University of York
11 March 2016 from 1:30 PM to 2:30 PM
339 Davey Laboratory
Contact Name
Jun Zhu
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Recent progress in engineering of enhanced spin-orbit coupling in graphene through addition of impurities and proximity effect to suitable substrates has opened up intriguing possibilities [1]. The presence of sizeable spin–orbit interactions is predicted to unlock a plethora of phenomena absent in pristine samples, including non-trivial Z2 topological phases [2]. Of particular interest are spin Hall effects, the set of relativistic spin–orbit coupling phenomena whereby charge currents propagating in nonmagnetic materials generate spin currents and vice versa. In addition to their fundamental interest, spin Hall effects are key ingredients in schemes for manipulation and inter-conversion of spin and charge signals via pure electrical means, including spin Hall effect-induced spin–orbit torques at metal-ferromagnetic interfaces, and detection of spin currents generated from the spin Seebeck effect.  

Theory predicts that dilute adatoms inducing short-range spin–orbit interactions in graphene can trigger a robust and gate-tunable spin Hall effect through the resonant skew scattering mechanism [3]. This optimistic state of affairs is supported by recent experiments exploring non-local spin transport in H-bar graphene devices and spin pumping in graphene/magnetic insulator interfaces, thereby paving the way for all-electric spintronics in two-dimensional (2D) carbon platforms. This talk will survey the rich interplay between semiclassical and anomalous scattering mechanisms underlying the extrinsic spin Hall effect. The resonant scattering characteristic of 2D massless Dirac fermions, and its importance to the robustness of the spin Hall effect will be discussed. The last part of the talk will be devoted to the intriguing role played by quantum scattering mechanisms. Based on a nonperturbative diagrammatic calculation of the Kubo-Streda formula [4], I will argue that a spin Hall effect induced by quantum coherent skew scattering is within reach the current state of the art. 

[1] J. Balakrishnan et al. Nat. Comm. 5, 4748 (2014); A. Avsar et al. Nat. Comm. 5, 4875 (2014); Z. Wang et al., Nat. Comm. 6, 8339 (2015). J. Mendes et al. Phys. Rev. Lett. 115, 226601 (2015)

[2] C.L. Kane, and E.J. Mele, Phys. Rev. Lett. 95, 226801 (2005)

[3] A. Ferreira et al. Phys. Rev. Lett. 112, 066601 (2014)

[4] M. Milletari and A. Ferreira, arXiv pre-print: 1601.08076 (2016)