Electrode-tunable nonlocal Rashba-Edelstein effect and layer-selective chirality switch in WSe$_2$-intercalated bilayer graphene

Abstract

We show that intercalating a WSe$_2$ monolayer into bilayer graphene creates a synthetic bilayer graphene at the Fermi level, in which WSe$_2$-mediated wavefunction overlap hybridizes the two graphene layers, giving rise to states delocalized across both layers. Because the interlayer coupling is comparable in energy to the proximity-induced spin-orbit interaction, the resulting spintronic behavior goes beyond what is typically accessible in conventional single-interface proximity systems. A simple four-electrode device, with source and drain electrodes on both the top and bottom graphene layers, gives access to distinct regimes depending on which electrodes are activated. The most prominent feature is a nonlocal Rashba-Edelstein effect, activated via cross-layer source and drain electrodes, in which a charge current injected into one graphene layer generates a spin accumulation in the spatially separated opposite layer. This effect is robust to the twist angle modulation between graphene and WSe$_2$ and to the applied electric field, suggesting that a moderate degree of structural asymmetry along the vertical direction does not destroy it. In addition, activating the source and drain electrodes on either the top or bottom graphene layer reveals local Rashba-Edelstein signals of opposite sign in the two layers, thereby realizing a layer-selective chirality switch. This is a consequence of the hidden Rashba effect, which is present even when a net Rashba splitting is forbidden. Our results suggest new physical regimes and device architectures that could be useful for spintronic applications.