Quantum interference and spin transport in M-OPE molecular devices controlled by N or B atom substitution

Abstract

In this paper, the first-principles method based on density functional theory and non-equilibrium Green's function is used to investigates the modulation of quantum interference and spin transport in N and B atom substituted meta-phenylene (M-OPE) molecular devices. The zero bias spin transmission spectrum of M-OPE molecular devices shows that HOMO and LUMO are located at higher energy positions on both sides of the Fermi level, and there is a clear transmission spectrum valley (anti resonance peak) on the right side of the Fermi level. This indicates that M-OPE molecules are typical destructive quantum interference molecular systems. Research has found that N and B atoms replace carbon atoms at positions 1, 2, and 3 on the central ring of the molecule, which have different degrees of suppression on the original destructive quantum interference of M-OPE molecular devices. The substitution of N and B atoms at position 1 has no effect on the original destructive quantum interference of M-OPE molecular devices, while the substitution of N and B atoms at positions 2 and 3 significantly suppresses the original destructive quantum interference of M-OPE molecular devices. Therefore, there is a significant difference in the electrical conductivity of devices with N and B atoms at different positions, with the order of electrical conductivity values being N2＞N3＞N1 and B2＞B3＞B1. The study also found that the spin current value of devices with B atom substitution is significantly higher than that of devices with N atom substitution. After the substitution of B atom at position 2, the spin current value of the device under negative bias is significantly greater than that under positive bias, exhibiting a significant spin rectification effect. Based on the extended curled arrow rule proposed by Luke et al. to predict the behavior of quantum interference effects, we explain the physical mechanism by which N and B protons at different positions have different effects on the cancellation of quantum interference in M-OPE molecular devices. The results of the quantum interference and spin transport regulation of molecular systems by the substitution of B and N atoms obtained in this article can provide theoretical guidance for the further application of heterocyclic aromatic hydrocarbons in molecular electronics.