First-passage time theory of activated rate chemical processes in electronic molecular junctions

Abstract

Confined nanoscale spaces, electric fields and tunneling currents make the molecular electronic junction an experimental device for the discovery of new, out-of-equilibrium chemical reactions. Reaction-rate theory for current-activated chemical reactions is developed by combining a Keldysh nonequilibrium Green's functions treatment of electrons, Fokker-Planck description of the reaction coordinate, and Kramers' first-passage time calculations. The NEGF provide an adiabatic potential as well as a diffusion coefficient and temperature with local dependence on the reaction coordinate. Van Kampen's Fokker-Planck equation, which describes a Brownian particle moving in an external potential in an inhomogeneous medium with a position-dependent friction and diffusion coefficient, is used to obtain an analytic expression for the first-passage time. The theory is applied to several transport scenarios: a molecular junction with a single, reaction coordinate dependent molecular orbital, and a model diatomic molecular junction. We demonstrate the natural emergence of Landauer's blowtorch effect as a result of the interplay between the configuration dependent viscosity and diffusion coefficients. The resultant localized heating in conjunction with the bond-deformation due to current-induced forces are shown to be the determining factors when considering chemical reaction rates; each of which result from highly tunable parameters within the system.

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Cited by in corpus (8)

• Unraveling current-induced dissociation mechanisms in single-molecule junctions
• Nonequilibrium reaction rate theory: Formulation and implementation within the hierarchical equations of motion approach
• Current-induced bond rupture in single-molecule junctions: Effects of multiple electronic states and vibrational modes
• Current-induced forces in nanosystems: A hierarchical equations of motion approach
• Quantum transport in driven systems with vibrations: Floquet nonequilibrium Green's functions and the GD approximation
• Emergence of negative viscosities and colored noise under current-driven Ehrenfest molecular dynamics
• A physically realizable molecular motor driven by the Landauer blowtorch effect
• Mean First Passage Time of the Symmetric Noisy Voter Model with Arbitrary Initial and Boundary Conditions