Role of molecule-electrode coupling strength in inducing inelastic transmission spectra of Hf@C28

Abstract Herein, we report how tuning of molecule-electrode coupling strength can turn on the coupling of tunnelling electrons with vibrational modes of central molecule in the two-probe configuration of Hf@C28 self-assembled between two Au(111) electrodes and thereby activating inelastic transmission path. The in silico study compares quantum transport properties of optimized configuration having C-Au bond length of 2.01 A (weakly-bound), with strongly-bound configuration having C-Au bond length of 1.6 A. It is observed that in weak-coupling the inelastic transmission coefficient is insignificant, however with strong-coupling symmetric and asymmetric part of inelastic transmission together contributes to rise in inelastic current. This rise in inelastic current is attributed to the resonance of phononic vibration corresponding to low-energy phonon-mode and energy of tunnelling electron close to applied bias 0.15-0.25V. Observed results have been substantiated through an analysis of high density in-phase transmission pathways within the molecular part mediated by resonating electrons and phonon modes.