Adding spin degree of freedom to negative differential resistance (NDR)

What is it about?

Adding a spin degree of freedom to NDR may lead important applications including spin-resolved oscillators, amplifiers, switchings, and memories. In this work, we propose a bulk graphene based, spin- dependent double-barrier resonant tunneling diode, which requires only depositing two gated EuO strips on top of a sufficiently wide and short graphene sheet. Remarkably, we find a clear sign of spin selectivity and region tunability in the spin-dependent NDR: by changing the top gates hence the spin-dependent resonance levels in the device, the spin index of the NDR can be tuned as spin up only, spin down only, or both spins; meanwhile, the central position of the NDR region in each case can be monotonously tuned over a wide bias range.

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Why is it important?

The existing schemes require appropriate introduction of magnetic doping, defects, or superlattices in zigzag or armchair graphene nanoribbons, which make the experimental implementation of these devices rather hard. In our device, no specific control of the graphene edge type is needed because the transport is dominated by bulk states; no dopings or defects are required because the ferromagnetism is induced by magnetic insulators; and two ferromagnetic barriers instead of a ferromagnetic superlattice are enough because large energy gaps are induced. Together with the spin selectivity and region tunability, these relative ease in fabrication make the proposed device an important building block for future spintronic or NDR circuits.

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