Localized excitons in 1D half-filled paramagnetic Hubbard model

TL;DR

This paper investigates the formation and coexistence of localized electron pairs and excitons in the 1D Hubbard model, revealing a quantum transition driven by Coulomb interaction and topologically nontrivial electronic behavior.

Contribution

It provides an analytical and numerical analysis of the transition between doublon and exciton regimes in the Hubbard model, highlighting the role of effective hybridization.

Findings

Quantum transition from doublon to exciton regime with varying U

Topologically nontrivial electronic spectrum at the Fermi level

Hybridization of valence and conduction bands influences localization

Abstract

By the example of the Hubbard model we analytically and numerically examine the formating and coexisting of localized electron--electron pairs (doublons) and localized electron--hole pairs (Frenkel--type excitons) . Here we demonstrate that at a variation of the on-site Coulomb repulsion U there occurs a quantum transition from the doublon to the exciton regime that is conditioned by the low-energy effective hybridization of the valence and conductivity subbands. We calculate momentum distribution functions and electronic spectrum functions for different U, which reveal topologically nontrivial behaviour at the Fermi level.