Charge-state dependent vibrational relaxation in a single-molecule junction

Journal article

The outcome of an electron-transfer process is determined by the quantum-mechanical interplay between electronic and vibrational degrees of freedom. Nonequilibrium vibrational dynamics are known to direct electron-transfer mechanisms in molecular systems; however, the structural features of a molecule that lead to certain modes being pushed out of equilibrium are not well understood. Herein, we report on electron transport through a porphyrin dimer molecule, weakly coupled to graphene electrodes, that displays sequential tunneling within the Coulomb-blockade regime. The sequential transport is initiated by current-induced phonon absorption and proceeds by rapid sequential transport via a nonequilibrium vibrational distribution of low-energy modes, likely related to torsional molecular motions. We demonstrate that this is an experimental signature of slow vibrational dissipation, and obtain a lower bound for the vibrational relaxation time of 8 ns, a value dependent on the molecular charge state.

Authors: Bian, X; Chen, Z; Sowa, JK; Evangeli, C; Limburg, B

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: American Physical Society
• Journal: Physical Review Letters
• Volume: 129
• Issue: 20
• Article number: 207702
• Publication date: 2022-11-09
• Acceptance date: 2022-10-20
• DOI: 10.1103/PhysRevLett.129.207702
• EISSN: 1079-7114
• ISSN: 0031-9007
• Language: English
• Keywords: FFR