Charge-Transfer Excitations in One-Dimensional Dimerized Mott Insulators

TL;DR

This paper explores the optical excitations in 1D dimerized Mott insulators, classifying charge-transfer states and applying findings to understand photoinduced phase transitions in a specific organic material.

Contribution

It introduces a classification of charge-transfer states in 1D dimerized Mott insulators and applies this framework to interpret experimental observations in TTTA.

Findings

Identified three classes of charge-transfer states: interdimer unbound, interdimer exciton, intradimer exciton.

Found the lowest photoexcited state in TTTA is an interdimer CT exciton.

Determined the second lowest state in TTTA is an intradimer CT exciton.

Abstract

We investigate the optical properties of one-dimensional (1D) dimerized Mott insulators using the 1D dimerized extended Hubbard model. Numerical calculations and a perturbative analysis from the decoupled-dimer limit clarify that there are three relevant classes of charge-transfer (CT) states generated by photoexcitation: interdimer CT unbound states, interdimer CT exciton states, and intradimer CT exciton states. This classification is applied to understanding the optical properties of an organic molecular material, 1,3,5-trithia-2,4,6-triazapentalenyl (TTTA), which is known for its photoinduced transition from the dimerized spin-singlet phase to the regular paramagnetic phase. We conclude that the lowest photoexcited state of TTTA is the interdimer CT exciton state and the second lowest state is the intradimer CT exciton state.