An expandable kinetic Monte Carlo platform for modelling electron transport through chiral molecules

Abstract

Chirality from molecular structures interacts with the spin angular momentum of electrons and photons giving rise to a variety of interesting phenomena. Among these, the observation of spin selective transport at room temperature is particularly attractive for the development of functional spintronic devices. During the past twenty five years, two effects have attracted considerable experimental and theoretical attention: electric Magnetochiral Anisotropy (eMChA) and Chirality Induced Spin Selectivity (CISS). In spite of the large body of work devoted to these phenomena, there is still no clear agreement on their microscopic origin(s). It even remains an open question whether eMChA and CISS arise from fundamentally different mechanisms or whether they are different experimental manifestations of the same underlying microscopic effects. In this work, we have developed the core of an efficient kinetic Monte Carlo code for the modeling of electron transport under an applied voltage, where the alpha and beta spin channels are treated independently. Each transport channel is characterized through its intrinsic electron mobility and an effective coupling between charge motion, spin, and chirality. This framework makes it possible to quantify the spin filtering that emerges from the interplay of these properties. From a set of simple rules emerges a voltage- and field-dependent effect that vanishes at low bias and shows the asymmetry between positive and negative voltages that is typically reported in electrical magnetochiral anisotropy experiments. We then move on to relate the internal parameters of our code with parameterization that has been used to describe the eMChA effect.