[论文解读] An expandable kinetic Monte Carlo platform for modelling electron transport through chiral molecules

Silvia Giménez-Santamarina, Andrés Aragón Martínez+2 more|arXiv (Cornell University)|Jan 24, 2026

Molecular Junctions and Nanostructures被引用 1

一句话总结

本论文提出一个模块化的动力学蒙特卡洛框架，用来在偏压下建模自旋与手性相关的电子传输，从而可探索在手性分子中出现的 eMChA 与未来的 CISS 机制。

ABSTRACT

Molecular chirality interacting in a non-negligible manner with the spin angular momentum of subatomic particles, mainly electrons or photons, is the cause of a variety of spin-dependent filtering effects in quantum transport. Among them, spin-selective transport at room temperature is clearly one of the most promising properties in the quest for functional spintronic devices. In this context, two main effects have been experimentally investigated in the past 25 years and have attracted significant interest within the community: the so-called Electronic Magnetochiral Anisotropy (eMChA) and Chirality Induced Spin Selectivity (CISS). Despite extensive research, there is still a lack of consensus in the modeling of their microscopic mechanisms. As a consequence, it remains unclear whether the two are truly distinct or if they originate from a common physical cause. With the long-term goal of modelling the main different theories and to test them against the available experimental evidence, we programmed the core of an efficient kinetic Monte Carlo code. The current code models electron transport under an external voltage, distinguishes between $α$ and $β$ spin currents, and parametrizes molecules by their intrinsic electron mobility and the effective coupling between electron movement, spin and chirality. The code allows obtaining spin filtering values arising from the effective coupling between these three. We obtain an effect that vanishes at low voltages, with the asymmetry between positive and negative voltages typically found in electrical magnetochiral anisotropy experiments.

研究动机与目标

• 激励并验证一个微观、现象学模型，以描述在施加电压的手性系统中的自旋相关传输。
• 开发一个高效的 kMC 代码，包含自旋和手性耦合，并能再现基本的电阻行为与 eMChA 征象。
• 提供一个模块化框架，便于扩展以纳入额外的手性自旋传输理论，并可与实验数据进行基准比较。

提出的方法

• 在沿骨架的线性势能分布下，对一组相同分子链的集合进行外加电压的电子传输建模。
• 用固定自旋标签表示电子并跟踪自旋分辨跃迁事件以获得自旋电流。
• 通过一个符号因子 (-1)^{s·c·v} 将自旋、手性和传输方向纳入考虑，以捕捉磁手性对称性要求。
• 引入一个现象学的 eMChA 项，通过 tanh(qV/kBT) 的依赖来调制能量偏置，以再现电压依赖的自旋筛选。
• 通过在两端引流再重新注入电子来确保电流流动，从而定义净电流和饱和行为。
• 验证欧姆定律和电阻关系能够自然地从随机跳跃动力学中出现，而非强加宏观电路约束。

Figure 1: Current-voltage curve obtained from the kinetic Monte Carlo simulation for (red curve) and (purple curve) spin channels, together with the corresponding unpolarized current. The results are shown for a system comprising $N=5500$ electrons distributed over identical molecular strands, a dim

实验结果

研究问题

• RQ1 一个动力学蒙特卡洛框架是否能够再现手性分子系统的基本电阻传输行为（欧姆定律、长度依赖、温度依赖）？
• RQ2 自旋、手性和传输方向如何组合在施加偏压时产生类似 eMChA 的自旋相关传输？
• RQ3 一个模块化、可扩展的 kMC 平台是否能够充分捕捉磁手性效应的定性特征，并作为对比 CISS/eMChA 理论的测试平台？

主要发现

• 该模型在低电压下呈现与偏压成线性关系的电流，并随分子长度增加而下降，与类似欧姆行为一致。
• 电流大小随并联链数的增加而增强，等效地表现为横截面积。
• 自旋分辨电流随电压的变化而发散，原因在于与手性和传输方向相关的自旋依赖能项，产生类 eMChA 的不对称性。
• eMChA 分量在零电压时消失，随电压增大而增强，在高偏压时因 tanh 依赖而趋于饱和。
• 通过 tanh(V) 项的紧凑现象耦合，捕捉与磁手性效应相关的本质电压依赖自旋筛选。
• 该框架设计为易于扩展，以纳入额外的自旋动力学、外部场或替代理论机制。