手性介质中自旋相关电子传输的镜面对称性动态破缺导致对映体过量
Dynamic Breaking of Mirror Symmetry in Spin-Dependent Electron Transport through Chiral Media Causes Enantiomeric Excesses
AI总结：
本文通过实验、理论和计算证明，手性分子中自旋相关过程的效率差异（如总角动量矢量取向不同）可能导致对映体选择性，为自然界中特定同手性（如RNA的D型）的选择提供了可能解释。
摘要：
两个基本问题困扰了科学家150多年：生命如何变得同手性，以及为什么选择了这种特定的手性。最近研究表明，同手性可能通过分子与磁性基底的对映选择性相互作用而出现，这是由于RNA前体在早期地球丰富的磁铁矿基底上的不对称结晶。这一现象基于手性诱导的自旋选择性（CISS）效应。尽管该模型具有稳健性，但它未能回答第二个问题：为什么选择了特定的手性（RNA的D型）。在这里，我们证明自旋参与过程在手性分子的两个对映体中可能产生不同的结果。在具有未配对电子的手性分子中，或当电子通过它们时，总角动量矢量J沿易轴排列，该易轴由自旋-轨道耦合和分子场不对称性引起的磁各向异性定义。J的大小在两个对映体中相同，但矢量相对于分子框架的排列可能不同。这种差异可以通过例如J与分子电偶极矩之间的角度来量化。我们通过直接测量、理论和从头计算表明，手性分子中的动态自旋过程可能导致自旋相关现象（包括手性分子与磁性表面的相互作用）的效率不同。这些发现可能为自然界中特定的同手性提供解释。
英文摘要：
Two fundamental questions have puzzled scientists for more than 150 years. How did life become homochiral and why was this specific handedness selected. Recently, it has been shown that homochirality could have emerged through the enantioselective interactions of molecules with magnetic substrates due to the asymmetric crystallization of an RNA precursor on a magnetite substrate, abundant on early Earth. This phenomenon is based on the chirality-induced spin selectivity,CISS, effect. Despite its robustness, this model could not provide an answer to the second question: why one specific handedness, D for RNA, was selected. Here we demonstrate that spin-involving processes can have different outcomes in the two enantiomers of chiral molecules. In chiral molecules with unpaired electrons or while electrons are passing through them, the total angular momentum vector, J, is aligned along the easy axis, which is defined by the magnetic anisotropy induced by the spin-orbit coupling and asymmetry of the molecular field. The magnitude J is the same for both enantiomers, but the vectors may be aligned differently relative to the molecular frame in the two enantiomers. This difference can be quantified by, for example, by the angle between J and electric dipole moment of the molecule. We show by direct measurements, theory, and ab initio calculations that dynamic spin processes in chiral molecules could result in different efficiencies of spin-related phenomena, including the interaction of chiral molecules with magnetic surfaces. The findings may provide an explanation for the specific homochirality in nature.
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