Jaroslav Fabian: Electron spin in the 2D realm: proximity effects

Stacking graphene with other 2D materials opens up fascinating possibilities for spintronics, not feasible with conventional materials structures. Transition metal dichalcogenides are of particular interest due to their strong spin-valley coupling. Placing graphene on, say, MoS2, enables optospintronics [1], whereby optically generated spins in MoS2 are transferred into graphene. Even more fascinating are proximity effects allowing spin manipulation. Spin-valley locking in the substrate is manifested via the spin Zeeman splitting in graphene [2], which, in turn, yields giant spin relaxation anisotropy predicted in [3]. Since the structure of intrinsic spin-orbit coupling is dramatically altered by the proximity effect, novel pseudohelical edge states can emerge in graphene nanoribbons and flakes, protected against backscattering by time reversal symmetry [4], communicating between the edges by spin-flip wormhole tunneling reflectionless channels. Much greater playground for new physics is offered by bilayer graphene on 2D materials. Due to the short range of proximity effects, one can efficiently tune induced spin interactions via electric fields---gating. Thus, spin-orbit coupling can be turned on and off [5], opening prospects for novel spin transistors. I will also present latest results on spin relaxation anisotropy in encapsulated (by hBN) graphene.

References

[1] M. Gmitra and J. Fabian, Phys. Rev. B 92, 155403 (2015).

[2] M. Gmitra, D. Kochan, P. Högl, and J. Fabian, Phys. Rev. B 93, 155104 (2016).

[3] A. Cummings, J. Garcia, J. Fabian, and S. Roche, Phys. Rev. Lett. 119, 206601 (2017).

[4] T. Frank, P. Högl, M. Gmitra, D. Kochan, and J. Fabian, Phys. Rev. Lett 120, 156402 (2018).

[5] M. Gmitra and J. Fabian, Phys. Rev. Lett. 119, 146401 (2017).