Strong Electron-Vibration Signals in Weakly Coupled Molecular Junctions: Activation of Spin-Crossover.

Zhang, Yachao; Giménez-Santamarina, Silvia; Cardona-Serra, Salvador; Gao, Fei; Coronado, Eugenio; Brandbyge, Mads · Nano Lett · 2024

basic_science · Level V

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Abstract

Manipulating individual molecular spin states with electronic current has the potential to revolutionize quantum information devices. However, it is still unclear how a current can cause a spin transition in single-molecule devices. Here, we propose a spin-crossover (SCO) mechanism induced by electron-phonon coupling in an iron(II) phthalocyanine molecule situated on a graphene-decoupled Ir(111) substrate. We performed simulations of both elastic and inelastic electron tunneling spectroscopy (IETS), which reveal current-induced Fe-N vibrations and an underestimation of established electron-vibration signals. Going beyond standard perturbation theory, we examined molecules in various charge and spin states using the Franck-Condon framework. The increased probability of spin switching suggests that notable IETS signals indicate SCO triggered by the inelastic vibrational excitation associated with Fe-N stretching.