Non-adiabatic effects of nuclear motion in quantum transport of electrons: a self-consistent Keldysh–Langevin study

Kershaw, Vincent F., and Kosov, Daniel S. (2020) Non-adiabatic effects of nuclear motion in quantum transport of electrons: a self-consistent Keldysh–Langevin study. Journal of Chemical Physics, 153. 154101.

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Abstract

The molecular junction geometry is modeled in terms of nuclear degrees of freedom that are embedded in a stochastic quantum environment of non-equilibrium electrons. The time-evolution of the molecular geometry is governed via a mean force, a frictional force, and a stochastic force, forces arising from many electrons tunneling across the junction for a given nuclear vibration. Conversely, the current-driven nuclear dynamics feed back to the electronic current, which can be captured according to the extended expressions for the current that have explicit dependences on classical nuclear velocities and accelerations. Current-induced nuclear forces and the non-adiabatic electric current are computed using non-equilibrium Green’s functions via a timescale separation solution of Keldysh–Kadanoff–Baym equations in the Wigner space. Applying the theory to molecular junctions demonstrated that non-adiabatic corrections play an important role when nuclear motion is considered non-equilibrium and, in particular, showed that non-equilibrium and equilibrium descriptions of nuclear motion produce significantly different current characteristics. It is observed that non-equilibrium descriptions generally produce heightened conductance profiles relative to the equilibrium descriptions and provide evidence that the effective temperature is an effective measure of the steady-state characteristics. Finally, we observe that the non-equilibrium descriptions of nuclear motion can give rise to the Landauer blowtorch effect via the emergence of multi-minima potential energy surfaces in conjunction with non-uniform temperature profiles. The Landauer blowtorch effect and its impact on the current characteristics, waiting times, and the Fano factor are explored for an effective adiabatic potential that morphs between a single, double, and triple potential as a function of voltage.

Item ID: 65710
Item Type: Article (Research - C1)
ISSN: 1089-7690
Copyright Information: © 2020 Author(s). Published under license by AIP Publishing.
Date Deposited: 15 Feb 2021 05:56
FoR Codes: 51 PHYSICAL SCIENCES > 5102 Atomic, molecular and optical physics > 510201 Atomic and molecular physics @ 100%
SEO Codes: 97 EXPANDING KNOWLEDGE > 970102 Expanding Knowledge in the Physical Sciences @ 100%
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