  We predict that vertical transport in heterostructures formed by twisted
graphene layers can exhibit a unique bistability mechanism. Intrinsically
bistable $I$-$V$ characteristics arise from resonant tunneling and interlayer
charge coupling, enabling multiple stable states in the sequential tunneling
regime. We consider a simple trilayer architecture, with the outer layers
acting as the source and drain and the middle layer floating. Under bias, the
middle layer can be either resonant or non-resonant with the source and drain
layers. The bistability is controlled by geometric device parameters easily
tunable in experiments. The nanoscale architecture can enable uniquely fast
switching times.
