Chirality has been a property of central importance in physics, chemistry and biology for more than a century. Recently, electrons were found to become spin polarized after transmitting through chiral molecules, crystals, and their hybrids. This phenomenon, called chirality-induced spin selectivity (CISS), presents broad application potentials and far-reaching fundamental implications involving intricate interplays among structural chirality, topological states, and electronic spin and orbitals. However, the microscopic picture of how chiral geometry influences electronic spin remains elusive, given the negligible spin-orbit coupling (SOC) in organic molecules. In this work, we address this issue via a direct comparison of magnetoconductance (MC) measurements on magnetic semiconductor-based chiral molecular spin valves with normal metal electrodes of contrasting SOC strengths. The experiment reveals that a heavy-metal electrode provides SOC to convert the orbital polarization induced by the chiral molecular structure to spin polarization. Our results illustrate the essential role of SOC in the metal electrode for the CISS spin valve effect. A tunneling model with a magnetochiral modulation of the potential barrier is shown to quantitatively account for the unusual transport behavior.

一个多世纪以来，手性一直是物理学、化学和生物学中至关重要的性质。最近，人们发现电子在穿过手性分子、晶体及其混合物后会发生自旋极化。这种现象被称为手性诱导自旋选择性（CISS），具有广泛的应用潜力和深远的基本影响，涉及结构手性、拓扑态以及电子自旋和轨道之间复杂的相互作用。然而，考虑到有机分子中的自旋轨道耦合（SOC）可以忽略不计，手性几何如何影响电子自旋的微观图景仍然难以捉摸。在这项工作中，我们通过直接比较基于磁性半导体的手性分子自旋阀与具有对比 SOC 强度的普通金属电极的磁导 (MC) 测量来解决这个问题。实验表明，重金属电极提供SOC，将手性分子结构引起的轨道极化转化为自旋极化。我们的结果说明了 SOC 在金属电极中对于 CISS 自旋阀效应的重要作用。具有势垒磁手性调制的隧道模型被证明可以定量地解释不寻常的传输行为。