Influence of Nonequilibrium Vibrational Dynamics on Spin Selectivity in Chiral Molecular Junctions

TL;DR

This paper investigates how nonequilibrium molecular vibrations influence the spin selectivity effect in chiral molecular junctions, revealing that vibrational dynamics drive the CISS phenomenon through a combined quantum-classical modeling approach.

Contribution

It introduces a new vibrational displacement polarization metric and demonstrates the dynamic correlation between vibrational polarization and spin selectivity in molecular nanojunctions.

Findings

Vibrational dynamics are crucial for spin selectivity in chiral molecules.

Spin selectivity correlates with vibrational polarization over time.

Temperature and voltage influence the vibrationally driven CISS effect.

Abstract

We explore the role of molecular vibrations in the chirality-induced spin selectivity (CISS) effect in the context of charge transport through a molecular nanojunction. We employ a mixed quantum-classical approach that combines Ehrenfest dynamics for molecular vibrations with the hierarchical equations of motion method for the electronic degrees of freedom. This approach treats the molecular vibrations in a nonequilibrium manner, which is crucial for the dynamics of molecular nanojunctions. To explore the effect of vibrational dynamics on spin selectivity, we also introduce a new figure of merit, the displacement polarization, which quantifies the difference in vibrational displacements for opposing lead magnetizations. We analyze the dynamics of single trajectories, investigating how the spin selectivity depends on voltage and electronic-vibrational coupling. Furthermore, we investigate the dynamics and temperature dependence of ensemble-averaged observables. We demonstrate that spin selectivity is correlated in time with the vibrational polarization, indicating that dynamics of the molecular vibrations is the driving force of CISS in this model within the Ehrenfest approach.