Efficient dual spin-valley filter in strained silicene

Abstract

We propose a highly efficient dual spin-valley filter in silicene, consisting of two distinct regions. In the first region, angular separation of the two valley spins in momentum-space is induced by a uniaxial strain, with further spin separation induced by an exchange field. The second region acts as an extractor of the requisite spin-valley current by means of localized fringe magnetic fields and gate modulation of the electrical potential. We demonstrated controllable and highly-efficient filtering (exceeding 90%) for all four spin-valley combinations based on realistic parameter values. We also discussed the feasibility of practical realization of the silicene-based spin-valley filter.The linear Dirac-like energy momentum dispersion of graphene has been instrumental for many spintronic and valleytronic applications. 1-3) The utility of the Dirac dispersion has motivated a similar quest in silicene, which shares the same monolayer-honeycomb structure as graphene, but having heavier silicon atoms and consequently larger spin-orbit coupling. [4][5][6] In addition, silicene has the added attraction both theoretically 7) and experimentally 8) of real-and valley-spin dependence in its dispersion and transport properties, on account of its slightly buckled lattice. The inequivalent valleys K and K ′ at the corners of the reciprocal hexagonal lattice may be utilized in valleytronic applications. Recently, it was shown that application of strain which distorts the coupling strengths within the honeycomb lattice will also result in a valley-dependent gauge potential. 9-11) This valley-dependent effect of strain on the electrical properties of graphene has been investigated and proposed in several application such as the quantized valley hall effect, 12) modulations of I-V characteristic of nanoribbons 13) and valley filtering in graphene. 14) In practice, the controllable strain can be generated by depositing onto stretchable substrates [15][16][17] and free suspension across trenches. 18) The dependence on both the valley-spin and real-spin degrees of freedom of electron transport in silicene suggests the possibility of inducing spin-valley polarized current in the material. Such spin and valley polarization of current has been achieved magneto-optically. 19) An electrical method of inducing spin-valley polarization has been proposed by means of a Y-shaped spin-valley device. 20)Similarly, a spin filter based on two dimensional U-shaped device 21) and a three terminal Y-shaped

Perfect valley filter in strained graphene with single barrier region

“…In the literature, several valley filter applications have been proposed. [9][10][11][12][13] However, they have some limitations such as practical difficulties and low filter efficiency, as reported in Ref. 11 and Ref.…”

Klein tunneling in Weyl semimetals under the influence of magnetic field

“…Another option to achieve square shape magnetic vector potential may be using a single ferromagnetic strip whose magnetization is in the in-plane direction33. These type of magnetic barriers, i.e., square shape gauge potential, would be useful for electron filtering according to their incident angle when they are combined with another effect (e.g., strain) that can lift the valley or spin degeneracy, as investigated in several previous studies3334353637. Another work38 investigates the combined effects of magnetic and electrostatic potential barriers, in either the symmetric or antisymmetric configuration, on the transport properties of graphene.…”

Strain control of real- and lattice-spin currents in a silicene junction

“…Important for applications of electro-mechanical devices, spin and valley currents in silicene based junction under the influence of strain have been investigated [26,27]. Similar to graphene, strain in silicene may behave like pseudo vector potentials due to distortion of honeycomb atomic structure.…”

“…Similar to graphene, strain in silicene may behave like pseudo vector potentials due to distortion of honeycomb atomic structure. The effect of strain on spin and valley-dependent transmissions in silicene was studied [26]. Spin and valley transports in dual-gated silicene junction have been also studied [27].…”