Spin selectivity through time-reversal symmetric helical junctions
Spin selectivity through time-reversal symmetric helical junctions
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DOI：
10.1103/physrevb.102.035445
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发表时间：
2020-05
影响因子：
3.7
通讯作者：
Y. Utsumi;O. Entin-Wohlman;A. Aharony
中科院分区：
文献类型：
--
作者：
Y. Utsumi;O. Entin-Wohlman;A. Aharony
分析了通过一个由两个轨道通道和两个引线连接的分子的时间反演对称电荷和自旋输运。它表明，自旋分辨电流产生时，自旋翻转过程伴随着翻转的轨道通道。这一令人惊讶的发现并不与巴达尔森定理相矛盾[J. H. Bardarson，J. Phys. A：Math. Theor. 41，405203（2008）]：传输确实具有两对双退化本征值，如定理所要求的。自旋过滤效应明确证明了一个两端手性分子结，模拟与原子内自旋轨道相互作用（SOI）的双轨道紧束缚链。在通过有机分子如DNA的传输的背景下，这种效应被称为“手性诱导的自旋选择性”（CISS）。该模型表现出自旋分裂没有打破时间反演对称性：原子内SOI诱导伴随的自旋和轨道翻转。从无限大分子中布洛赫态的角度来考察这些跃迁，结果表明，它们会导致布洛赫波数的变化，其大小为单圈的倒数，其方向取决于螺旋的左手性和右手性。结果，自旋向上和自旋向下的状态在相反的方向上传播，导致CISS效应。为了进一步证实我们的图片，我们提出了一个分析听话的表达这样的（单）分子的散射矩阵。
Time-reversal symmetric charge and spin transport through a molecule comprising two-orbital channels and connected to two leads is analyzed. It is demonstrated that spin-resolved currents are generated when spin-flip processes are accompanied by a flip of the orbital channels. This surprising finding does not contradict Bardarson's theorem [J. H. Bardarson, J. Phys. A: Math. Theor. 41, 405203 (2008)] for two-terminal junctions: the transmission does possess two pairs of doubly-degenerate eigenvalues as required by the theorem. The spin-filtering effect is explicitly demonstrated for a two-terminal chiral molecular junction, modeled by a two-orbital tight-binding chain with intra-atomic spin-orbit interactions (SOI). In the context of transport through organic molecules like DNA, this effect is termed "chirality-induced spin selectivity" (CISS). The model exhibits spin-splitting without breaking time-reversal symmetry: the intra-atomic SOI induces concomitant spin and orbital flips. Examining these transitions from the point of view of the Bloch states in an infinite molecule, it is shown that they cause shifts in the Bloch wave numbers, of the size of the reciprocal single turn, whose directions depend on the left-and right-handedness of the helix. As a result, spin-up and spin-down states propagate in the opposite directions, leading to the CISS effect. To further substantiate our picture, we present an analytically-tractable expression for the 8$\times$8 scattering matrix of such a (single) molecule.