"Graphene under lateral spin-orbit-coupled superlattice potentials - Berry curvature and spin-Hall current routing"

Abstract

The spin-orbit coupling has attracted enormous attention due to its central role in topological insulating phases and low-power charge-to-spin conversion with potential applications in next-generation spintronic devices [1]. Recently, atomically thin heterostructures built from graphene and semiconducting dichalcogenides have emerged as strong contenders for fundamental studies of spin-dependent phenomena [2, 3]. Here, we show that lateral spin-orbit-coupled superlattice potentials applied to graphene sheets drastically impact the topological character of 2D Dirac electronic states, leading to the emergence of anisotropic Berry curvature hotspots that can be used to control spin currents. The spatial modulation of the spin- orbit coupling envisaged theoretically in this work could be realised by proximity effect to rippled groupVI dichalcogenide substrates [4]. The spin-Hall angle, which measures the charge-to-spin current conversion efficiency, is found to change sign with a reversal of the lateral gate voltage, allowing all-in-one activation and routing of spin Hall currents with electrostatic control. Our work answers important questions on the effect of spin-orbit patterning in nanostructures and suggests that tuneable Dirac superlattices will be important components in ultra-low-power spin transistors built from two-dimensional materials. References [1] A. Soumyanarayanan et al. Nature 539, 509 (2016). [2] M. Offidani, M. Milletari, R. Raimondi & A. Ferreira. Phys. Rev. Lett. 119, 196801 (2017). [3] M. Offidani and A. Ferreira. Phys. Rev. B 98, 245408 (2018). [4] Z. Wang ET AL. Phys. Rev. X 6, 041020 (2016).