Femtosecond dynamics and laser control of charge transport in trans-polyacetylene

TL;DR

This study investigates femtosecond laser control of charge transport in trans-polyacetylene, revealing how vibronic couplings affect electronic coherence and demonstrating limited but feasible control using ultrafast pulses.

Contribution

It provides a detailed quantum-classical simulation of femtosecond charge dynamics in conjugated polymers under coherent laser control, accounting for vibronic effects.

Findings

Vibronic couplings alter the electronic spectrum and cause ultrafast decoherence.

Limited coherent control remains possible with pulses comparable to electronic dephasing times.

Simulations realistically describe femtosecond vibronic dynamics in complex conjugated systems.

Abstract

The induction of dc electronic transport in rigid and flexible trans-polyacetylene oligomers according to the $\omega$ vs. $2\omega$ coherent control scenario is investigated using a quantum-classical mean field approximation. The approach involves running a large ensemble of mixed quantum-classical trajectories under the influence of $\omega+2\omega$ laser fields, and choosing the initial conditions by sampling the ground-state Wigner distribution function for the nuclei. The vibronic couplings are shown to change the mean single-particle spectrum, introduce ultrafast decoherence, and enhance intramolecular vibrational and electronic relaxation. Nevertheless, even in the presence of significant couplings, limited coherent control of the electronic dynamics is still viable, the most promising route involving the use of fs pulses with a duration that is comparable to the electronic dephasing time. The simulations offer a realistic description of the behavior of a simple coherent control scenario in a complex system, and provide a detailed account of the femtosecond photoinduced vibronic dynamics of a conjugated polymer.