Switching Quantum Interference in Phenoxyquinone Single Molecule Junction with Light

Abstract

Quantum interference (QI) can lead to large variations in single molecule conductance. However, controlling QI using external stimuli is challenging. The molecular structure of phenoxyquinone can be tuned reversibly using light stimulus. In this paper, we show that this can be utilized to control QI in phenoxyquinone derivatives. Our calculations indicate that, as a result of such variation in molecular structure of phenoxyquinone, a crossover from destructive to constructive QI is induced. This leads to a significant variation in the single molecule conductance by a couple of orders of magnitude. This control of QI using light is a new paradigm in photosensitive single molecule switches and opens new avenues for future QI-based photoswitches.

Keywords: electrical conductance; molecular electronics; photochromic molecules; photoswitches; quantum interference.

Figure 1

Chemical structures of (a) trans and (b) cis phenoxyquinone isomers. In visible light, phenoxyquinone molecule takes trans configuration, whereas, under UV light, it is changed to cis confirmation.

Figure 2

Molecular structures of (a) trans and (b) cis isomers of phenoxyquinone with thiol anchor connected to gold electrodes, (c) low temperature conductance and (d) room temperature current for (a,b). Dashed lines in (c) show the corresponding room temperature conductances.

Figure 3

Molecular structures of (a) trans and (b) cis isomers of phenoxyquinone with acetylene linker and direct Au-C connection to gold electrodes; (c) low temperature conductance and (d) room temperature current for (a,b). Dashed lines in (c) show the corresponding room temperature conductances.

Figure 4

QI based on curly arrows rules and tight binding model. Arrow-pushing pathways for (a) cis and (b) trans phenoxyquinone isomers. (c,d) simplified tight binding picture and (e) electron transmission coefficient curves for trans and cis isomers as a function of electron energy for tight-binding model of site energy ε₀ = 0 and nearest-neighbor couplings γ = −1. On-site energy at red sites (Figure 4) is ε_m = −0.55γ and γ_m = −0.15.