Real-time density matrix renormalization group dynamics of spin and charge transport in push-pull polyenes and related systems

TL;DR

This study uses time-dependent density matrix renormalization group methods to analyze how terminal substituents influence spin and charge transport in push-pull polyenes, revealing that end groups mainly affect charge transfer amounts.

Contribution

It introduces a detailed real-time analysis of spin and charge dynamics in push-pull polyenes using advanced numerical techniques, comparing these with PMI systems to highlight differences.

Findings

End groups do not significantly alter spin and charge velocities.

Charge transport is affected by terminal substituents.

Spin and charge dynamics in PMI differ markedly from push-pull polyenes.

Abstract

In this paper we investigate the effect of terminal substituents on the dynamics of spin and charge transport in donor-acceptor substituted polyenes ($D-(CH)_{x}-A$) chains, also known as push-pull polyenes. We employ long-range correlated model Hamiltonian for the $D-(CH)_{x}-A$ system, and time-dependent density matrix renormalization group technique for time propagating the wave packet obtained by injecting a hole at a terminal site, in the ground state of the system. Our studies reveal that the end groups do not affect spin and charge velocities in any significant way, but change the amount of charge transported. We have compared these push-pull systems with donor-acceptor substituted polymethine imine (PMI), $D-(CHN)_{x}-A$, systems in which besides electron affinities, the nature of $p_{z}$ orbitals in conjugation also alternate from site to site. We note that spin and charge dynamics in the PMIs are very different from that observed in the case of push-pull polyenes, and within the time scale of our studies, transport of spin and charge leads to the formation of a "quasi-static" state.