Scattering theory of spin-orbit active adatoms on graphene
Scattering theory of spin-orbit active adatoms on graphene
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DOI：
10.1103/physrevb.90.035444
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发表时间：
2014-03
影响因子：
3.7
通讯作者：
A. Pachoud;Aires Ferreira;B. Ozyilmaz;A. Neto
中科院分区：
文献类型：
--
作者：
A. Pachoud;Aires Ferreira;B. Ozyilmaz;A. Neto
从理论上研究了二维无质量狄拉克费米子在石墨烯上的自旋-轨道相互作用的散射。石墨烯和附着原子轨道之间的杂化提升了原始宿主材料的自旋和谷简并，产生了丰富的自旋轨道耦合机制，其特征由蜂窝晶格上的确切吸附位置（桥、空心或顶部位置）和附着原子的外壳轨道类型决定。有效的纯石墨烯哈密顿量来源于对称考虑，而微观紧密结合方法将有效的低能耦合和石墨烯-杂化参数联系起来。在$T$矩阵的形式下，建立了涉及石墨烯载流子和自旋轨道活性原子的（自旋依赖的）散射事件的理论。与腔内散射和谷间散射相关的自旋电流被发现倾向于相互对立。我们建立了在一定条件下，空心位置的附着原子通过斜散射产生自旋霍尔效应，而顶部位置的附着原子通过三角电位散射产生横向电荷流。我们还确定了自旋霍尔效应显著增强的临界费米能量范围，并且相关的横向自旋电流可以逆转。
The scattering of two-dimensional massless Dirac fermions from local spin-orbit interactions with an origin in dilute concentrations of physisorbed atomic species on graphene is theoretically investigated. The hybridization between graphene and the adatoms' orbitals lifts spin and valley degeneracies of the pristine host material, giving rise to rich spin-orbit coupling mechanisms with features determined by the exact adsorption position on the honeycomb lattice---bridge, hollow, or top position---and the adatoms' outer-shell orbital type. Effective graphene-only Hamiltonians are derived from symmetry considerations, while a microscopic tight-binding approach connects effective low-energy couplings and graphene-adatom hybridization parameters. Within the $T$-matrix formalism, a theory for (spin-dependent) scattering events involving graphene's charge carriers, and the spin-orbit active adatoms is developed. Spin currents associated with intravalley and intervalley scattering are found to tend to oppose each other. We establish that under certain conditions, hollow-position adatoms give rise to the spin Hall effect, through skew scattering, while top-position adatoms induce transverse charge currents via trigonal potential scattering. We also identify the critical Fermi energy range where the spin Hall effect is dramatically enhanced, and the associated transverse spin currents can be reversed.