Localized polarons and doorway vibrons in finite quantum structures

TL;DR

This paper investigates how local vibrational modes influence electron transport in finite quantum structures, revealing regimes of vibration-assisted tunneling and polaron localization through exact numerical analysis.

Contribution

It introduces a detailed study of the Holstein-Hubbard model with site-dependent potentials, highlighting the conditions leading to different transport regimes in quantum systems.

Findings

Vibration-mediated tunneling observed at certain parameters.

Intrinsic polaron localization occurs under specific conditions.

Distinct signatures in density correlations, mobility, and optical response.

Abstract

We consider transport through finite quantum systems such as quantum barriers, wells, dots or junctions, coupled to local vibrational modes in the quantal regime. As a generic model we study the Holstein-Hubbard Hamiltonian with site-dependent potentials and interactions. Depending on the barrier height to electron-phonon coupling strength ratio and the phonon frequency we find distinct opposed behaviors: Vibration-mediated tunneling or intrinsic localization of (bi)polarons. These regimes are strongly manifested in the density correlations, mobility, and optical response calculated by exact numerical techniques.