Spin transistors built on 2D van der Waals heterostructures

A transistor based on spin rather than charge (spin transistor) was first proposed by Datta and Das in 1990. Such a spin-based device promises non-volatile data storage and a faster and more energy-efficient performance than present transistors. Many approaches have been pursued to realize spin transistors, but they remain a formidable challenge. Recent discovery of two-dimensional magnetic insulators such as CrI₃ with electrically switchable magnetic order and effective spin filtering effect inspires a new operational principle for spin transistors. Here we demonstrate spin field-effect transistors based on dual-gated graphene/CrI₃/graphene tunnel junctions. These devices show an ambipolar behavior and tunnel conductance that is dependent on the magnetic order in the CrI₃ tunnel barrier. The gate voltage switches the tunnel barrier between an interlayer antiferromagnetic and ferromagnetic state under a constant magnetic bias near the spin-flip transition, thus effectively altering the device between a low and a high conductance state with a large hysteresis. Based on the electrically controlled spin-flip transition in the magnetic tunnel barrier, these new spin transistors achieve spin injection, control and detection in a single device with a conductance ratio approaching 400%.