Spin-selectable, region-tunable negative differential resistance in graphene double ferromagnetic barriers

We propose a graphene device that can generate spin-dependent negative differential resistance (NDR). The device is composed of a sufficiently wide and short graphene and two gated EuO strips deposited on top of it. This scheme avoids graphene edge tailors required by previous proposals. More importantly, we find clear significant of a spin selectivity and a region tunability in the spin-dependent NDR: by changing the top gates of the device, NDR for spin up only, spin down only, or both spins (occurring sequentially) can be respectively realized; meanwhile, the central position of the NDR region in each case can be monotonously tuned in a wide range of bias voltage. These remarkable features are attributed to a gate controllability of the spin-dependent resonant levels in the device hence their deviations from the Fermi energy and Dirac point in the source electrode, respectively. They add a spin and a bias degree of freedom to conventional NDR-based devices, which paves a way for designing a whole new class of NDR circuits.