Long-Range Non-Equilibrium Coherent Tunneling Induced by Fractional Vibronic Resonances

TL;DR

This paper reveals how fractional vibronic resonances enable long-range coherent tunneling in molecular chains under energy bias, challenging traditional linear response and polaron models.

Contribution

It introduces the concept of fractional vibronic resonances causing long-range tunneling, supported by theoretical and model calculations, expanding understanding of vibronic effects in quantum transport.

Findings

Resonance occurs at fractional ratios of bias to phonon energy.

Long-range $n$-bond $m$-phonon tunneling is observed.

Model calculations match experimental Cy3 system results.

Abstract

We study the influence of a linear energy bias on a non-equilibrium excitation on a chain of molecules coupled to local phonons (a tilted Holstein model) using both a random-walk rate kernel theory and a nonperturbative, massively parallelized adaptive-basis algorithm. We uncover structured and discrete vibronic resonance behavior fundamentally different from both linear response theory and homogeneous polaron dynamics. Remarkably, resonance between the phonon energy $\hbar\omega$ and the bias $\delta_\epsilon$ occurs not only at integer but also fractional ratios $\delta_\epsilon/(\hbar\omega) = \frac{m}{n}$, which effect long-range $n$-bond $m$-phonon tunneling. These observations are also reproduced in a model calculation of a recently demonstrated Cy3 system. Potential applications range from molecular electronics to optical lattices and artificial light harvesting via vibronic engineering of coherent quantum transport.