Numerically exact, time-dependent treatment of vibrationally coupled electron transport in single-molecule junctions

TL;DR

This paper introduces a numerically exact ML-MCTDH method to study vibrational effects on electron transport in single-molecule junctions, revealing the dynamic formation of polaron states and phonon blockade phenomena.

Contribution

The paper develops and applies a novel ML-MCTDH approach within second quantization to accurately simulate vibrationally coupled electron transport in molecular junctions.

Findings

Vibrational motion significantly influences electron transport.

Polaron formation leads to current suppression (phonon blockade).

Dynamical vibrational effects are essential for accurate modeling.

Abstract

The multilayer multiconfiguration time-dependent Hartree (ML-MCTDH) theory within second quantization representation of the Fock space, a novel numerically exact methodology to treat many-body quantum dynamics for systems containing identical particles, is applied to study the effect of vibrational motion on electron transport in a generic model for single-molecule junctions. The results demonstrate the importance of electronic-vibrational coupling for the transport characteristics. For situations where the energy of the bridge state is located close to the Fermi energy, the simulations show the time-dependent formation of a polaron state that results in a pronounced suppression of the current corresponding to the phenomenon of phonon blockade. We show that this phenomenon cannot be explained solely by the polaron shift of the energy but requires methods that incorporate the dynamical effect of the vibrations on the transport. The accurate results obtained with the ML-MCTDH in this parameter regime are compared to results of nonequilibrium Green's function (NEGF) theory.