engleski

Efficient spin gating with van der Waals heterostructures

Efficient spin gating with van der Waals heterostructures We consider a possibility of operation of a device by which spin polarization of the current passing through it can be modified significantly using small electric fields, that is by which spin currents can be efficiently gated. Such a device could potentially find place as a building block for high performance spintronic devices [1]. The core of device would be an interface between a ferromagnetic metal (e.g. cobalt) and graphene. The small density of states (DOS) of graphene near the Fermi level and its two-dimensional nature would cause a significant shift in DOS at the Fermi level, and hence conductivity, in response to even the small gate electric fields, while the magnetic proximity effect would ensure that the shift is spin dependent. We find, however, that graphene and cobalt bind chemically and thus convenient electronic structure of graphene is lost, making the desired response to the electric field absent [1]. To preserve graphene's electronic structure, as well as keep the desired spin dependent response, we find it sufficient to add an additional layer of two-dimensional insulator, such as hexagonal boron nitride, between the metal and graphene [1] to which graphene would bind by van der Waals force. Still, because of the strong doping of graphene because of the chemical potential equilibration, the shift in the spin components of DOS at small external fields in such a metal - van der Waals heterostructure interface is not large enough for gating to be efficient. To counteract this unwanted doping we added a platinum layer to the structure, in two different configurations. The effect of the platinum layer seems favorable for intended application in both of them. The open questions are the effect of the gate field on the structures with platinum, as well as more detailed calculation of conductivity in all proposed stuctures. References: [1] P. Lazić, K. D. Belaschenko, I. Žutić, Phys. Rev. B 93, 241401 (2016)

surfaces ; magnetism ; graphene ; proximity effect

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