Modulation of hybrid interface states and magnetoresistance in quantum interference systems via functional groups

Abstract

Exploring the law of hybrid interface states (HIS) to the spin-dependent transport properties in magnetic single-molecule junctions is extremely significant for developing organic spintronic devices. Utilizing the first-principles method, the quantum interference systems consisting of a class of anthraquinone-based molecules sandwiched between two ferromagnetic electrodes are constructed and related spin transport properties are theoretically investigated. By substituting neutral, electron-withdrawing, and electron-donating functional groups on the cross-conjugated sites, valid modulation of the HIS and their spin polarization (SP) are demonstrated, which are caused by the distinct shift of molecular orbitals and the induced overlap with HIS. Accordingly, the spin-dependent transport calculation shows that an enhanced tunneling magnetoresistance (TMR) at low bias voltage and a reversed TMR at high bias voltage are realized by using the electron-withdrawing groups. We provide direct evidence of the distinctive TMR effect as the change of molecular SP around the Fermi energy combined with the shift of destructive quantum interference (DQI) feature. This work supplies a novel way to modulate the spin-dependent transport in molecular junctions by manipulating the HIS and the DQI feature simultaneously.