High-Performance Single-Molecule Switch Designed by Changing Parity of Electronic Wave Functions via Intramolecular Proton Transfer

Abstract

Molecular switches, as one of the functional molecular components, play a vital role in nanoscale logic circuits. Here, the effect of intramolecular proton transfer on the current of single-molecule devices consisting of a keto or enol molecule sandwiched between two magnetic zigzag graphene nanoribbon (zGNR) electrodes is theoretically investigated. The keto and enol tautomers interconvert into each other by intramolecular proton transfer. The results show that the current of the keto molecular device is hardly observed, whereas that of the enol molecular device is significantly enhanced, demonstrating a highly efficient switching effect with the ON/OFF ratio up to 3.4 × 102. Moreover, spin currents of the device with an enol isomer display giant bipolar rectification, with the largest rectification ratio of 1.4 × 105 when the two zGNR electrodes are antiparallely spin-polarized. The underlying mechanism is attributed to the parity matching principle of electronic wave functions in the core molecule and zGNR electrodes. The intramolecular proton transfer completely changes the parity of the electronic wave functions of the core molecule, and the electron tunneling channels around the Fermi energy are thus largely modified, resulting in a significant ON/OFF switching ratio. This work develops a strategy for designing high-performance single-molecule switches.