Bipolar spin diode based on a bent graphene nanoribbon

Using the nonequilibrium Greenʹs function method, we investigate the bias-driven spin transport through a graphene nanoribbon device, which consists of a central bent junction coupled to a zigzag-edge source and an armchair-edge drain. Due to the zigzag-armchair structural transformation and the possible symmetry-matching between the bands of the source and drain, remarkable intrinsic spin rectification effects are observed, and the rectification coefficient depends strongly on the width of the drain. When the two electrodes with quite similar width are both transversely symmetrical and the drain is a semiconductor, the rectification coefficient could be up to 104%. Our results provide an efficient possibility for designing nanoscale spin rectifier, especially for bipolar spin diode.