Magnetic Proximity Effects in Two-Dimensional Materials*

Proximity effects can transform a given material through its adjacent regions to become superconducting, magnetic, or topologically nontrivial. In bulk materials, their size often dwarfs the lengths of proximity effects allowing their neglect. However, in 2D materials such as graphene, transition-metal dichalcogenides (TMDs) and 2D electron gas (2DEG), the situation is drastically different. Even short-range magnetic proximity effects exceed their thickness and strongly modify spin transport and optical properties[1,2]. Experimental confirmation[3] of our prediction for bias-controlled spin polarization reversal in Co/h-BN/graphene[1] suggests that magnetic proximity effects may overcome the need for an applied magnetic field and a magnetization reversal to implement spin logic[4]. In TMDs, where robust excitons dominate their optical response, magnetic proximity effects cannot be described by the single-particle description. We predict a conversion between optically inactive and active excitons by rotating the magnetization of the substrate[2]. Combined magnetic and superconducting proximity effects could enable elusive Majorana bounds states (MBS) for fault-tolerant quantum computing. Exchanging (braiding) MBS yields a noncommutative phase, a sign of non-Abelian statistics and nonlocal degrees of freedom protected from local perturbations. MBS could be manipulated and braided in proximity-induced superconductivity in a 2DEG with magnetic textures from the fringing fields of magnetic tunnel junctions[5,6].
1. P. Lazic, K.D. Belashchenko, I. Zutic, Phys. Rev. B 93, 241401(R) (2016)
2. B. Scharf et al., Phys. Rev. Lett. 119, 127403 (2017)
3. P. Asshoff et al., 2D Mater. 4, 031004 (2017); M. Gurram et al., Nat. Comm. 8, 248 (2017); J. Xu et al., preprint
4. H. Wen et al., Phys. Rev. Appl. 5, 044003 (2016)
5. G.L. Fatin et al., Phys. Rev. Lett. 117, 077002 (2016); A. Matos-Abiague et al., Solid State Commun. 262, 1 (2017)