Pure spin current injection in hydrogenated graphene structures

Article

关键词: BAND-GAP;    REVERSIBLE HYDROGENATION;    PHOTOELECTRONS;    POLARIZATION;   

DOI  :  10.1103/PhysRevB.96.195415

来源: SCIE

【 摘 要 】

We present a theoretical study of spin-velocity injection (SVI) of a pure spin current (PSC) induced by linearly polarized light that impinges normally on the surface of two 50% hydrogenated noncentrosymmetric two-dimensional (2D) graphene structures. The first structure, labeled Up and also known as graphone, is hydrogenated only on one side, and the second, labeled Alt, is 25% hydrogenated at both sides. The hydrogenation opens an energy gap on both structures. The PSC formalism has been developed in the length gauge perturbing Hamiltonian, and includes, through the single-particle density matrix, the excited coherent superposition of the spin-split conduction bands inherent to the noncentrosymmetric nature of the structures considered in this work. We analyze two possibilities: in the first, the spin is fixed along a chosen direction, and the resulting SVI is calculated; in the second, we choose the SVI direction along the surface plane, and calculate the resulting spin orientation. This is done by changing the energy h omega and polarization angle a of the incoming light. The results are calculated within a full electronic band structure scheme using the density functional theory (DFT) in the local density approximation (LDA). The maxima of the spin velocities are reached when h omega = 0.084 eV and alpha = 35. for the Up structure, and h omega = 0.720 eV and alpha = 150. for the Alt geometry. We find a speed of 668 and 645 km/s for the Up and the Alt structures, respectively, when the spin points perpendicularly to the surface. Also, the response is maximized by fixing the spin-velocity direction along a high-symmetry axis, obtaining a speed of 688 km/s with the spin pointing at 13. from the surface normal, for the Up, and 906 km/s and the spin pointing at 60. from the surface normal, for the Alt system. These speed values are orders of magnitude larger than those of bulk semiconductors, such as CdSe and GaAs, thus making the hydrogenated graphene structures excellent candidates for spintronics applications.

【 授权许可】

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