Fe_(3)GeTe_(2)/h-BN/石墨烯二维异质结器件中的高效率自旋注入

Efficient spin injection in Fe_(3)GeTe_(2)/h-BN/graphene heterostructure

最近,二维铁磁材料的发现加速了自旋电子学在超低功耗电子器件方面的应用.其中,Fe_(3)GeTe_(2)通过实验调控,比如界面层间耦合和离子液体调控,可以使其居里温度达到室温,具有广泛的应用前景.本文基于密度泛函理论与非平衡格林函数方法,研究了Fe_(3)GeTe_(2)/石墨烯二维异质结在有无氮化硼作隧穿层情况下的输运性质.结果表明:当Fe_(3)GeTe_(2)/石墨烯之间为透明接触时,由于电子轨道杂化,在±0.1 V偏压下可以实现有效的自旋注入.通过加入氮化硼作为隧穿层,则可以在更宽偏压范围[–0.3 V,0.3 V]内实现高效自旋隧穿注入;并且,由于Fe_(3)GeTe_(2)与石墨烯电子态在布里渊区的空间匹配程度取决于电子自旋方向,相应出现的自旋过滤效应导致了接近100%的自旋极化率.这些研究结果有望推动二维全自旋逻辑以及相关超低功耗自旋电子器件的发展.

Recently,the discovery of intrinsic two-dimensional(2D)ferromagnetism has accelerated the application of spintronics in ultra-low power electronic device.Particularly,the Curie temperature of Fe_(3)GeTe_(2)can be improved to room-temperature in several ways,such as interfacial exchange coupling and ionic liquid gating,which makes Fe_(3)GeTe_(2)desirable for the practical application.In this work,we investigate the transport properties of Fe_(3)GeTe_(2)/graphene heterostructures with or without h-BN layers by utilizing the density functional theory combined with nonequilibrium Green’s function method.The results show that due to electronic orbital hybridization,the spin can be effectively injected into graphene with±0.1 V bias at the transparent contact interface of Fe_(3)GeTe_(2)/graphene.What is more,the efficient spin tunneling injection can be achieved in a wider bias range[–0.3 V,0.3 V]by adding h-BN as a tunneling layer,where the spin filter effect that is induced by mismatched distribution of spin-dependent electronic states in the Brillouin zone,leads a spin polarizability to approach 100%.These results are helpful in the applications of 2D all-spin logic and the development of ultra-low power spintronic devices.