Quantum confinement effects on the ordering of the lowest-lying excited states in conjugated chains

TL;DR

This study uses advanced computational methods to analyze how quantum confinement influences the ordering of excited states in conjugated chains, revealing complex dependencies on system parameters and excitation localization.

Contribution

It applies the symmetrized density matrix renormalization group to the extended Hubbard-Peierls model, providing new insights into state ordering and crossover phenomena in conjugated systems.

Findings

U-crossover highlights ionic character differences between states

elta crossover depends on N and U/t

N-crossover shows localization differences at intermediate correlations

Abstract

The symmetrized density matrix renormalization group approach is applied within the extended Hubbard-Peierls model (with parameters U/t, V/t, and bond alternation \delta) to study the ordering of the lowest one-photon (1^{1}B^{-}_u) and two-photon (2^{1}A^{+}_g) states in one- dimensional conjugated systems with chain lengths, N, up to N=80 sites. Three different types of crossovers are studied, as a function of U/t, \delta, and N. The U-crossover emphasizes the larger ionic character of the 2A_g state compared to the lowest triplet excitation. The \delta crossover shows strong dependence on both N and U/t. The N-crossover illustrates the more localized nature of the 2A_g excitation relative to the 1B_u excitation at intermediate correlation strengths.