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中国物理学会期刊

锯齿型硅烯纳米带电场调控非绝热量子化自旋泵浦

Electrical controllable non-adiabatic quantum spin pumping in zigzag silicene nanoribbon

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  • 基于紧束缚近似模型和Keldysh非平衡格林函数方法,我们研究了锯齿型硅烯纳米带中的单参数非绝热量子化自旋泵浦现象.我们发现,由于其特殊的态密度,较低费米能下会出现两个电流峰,但是零能费米能下只有一个电流峰值.垂直电场能显著改变低能区左向/右向传输速度以及隧穿概率,且对两支自旋有相反的作用效果.因此施加垂直电场可以破坏光子辅助过程对称性,实现自旋极化电流.在零费米能下出现纯自旋流,改变频率实现极化度由1到-1改变.该研究有望实现基于硅烯纳米带的纯电学调控的量子化自旋泵浦.

     

    Based on the tight binding model and Keldysh non-equilibrium Green’s function method, we investigated the single parameter non-adiabatic quantum spin pumping phenomenon in zigzag silicene nanoribbon. Quantum pumping consists of two opposite photon-assisted processes, namely the photon-absorption process and the photon-excitation process, which can drive charge carriers flowing in opposite directions. The perpendicular electric field can significantly alter the leftwards/rightwards propagation velocity as well as the tunneling probability in the low-energy region but has opposite influence on the two spin species. Therefore, applying a vertical electric field can destroy the symmetry of the photon-assisted processes, where the leftwards/rightwards transmission of one spin species is enhanced/weakened while the situation is exactly the opposite for the other spin, resulting in spin polarized currents. The pure spin current can occur at zero Fermi energy and the spin polarization can be inverted from 1 to -1 by tuning the driving frequencies. This study is expected to achieve the electrical controllable quantum spin pumping based on silicene nanoribbon, independent of any ferromagnetic elements.

     

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