Excitonic optical spectra and energy structures in a one-dimensional Mott insulator demonstrated by applying a many-body Wannier functions method to a charge model

TL;DR

This paper uses a many-body Wannier functions method to calculate excitonic optical spectra and energy structures in a 1D Mott insulator, successfully reproducing experimental data and revealing weakly bound excitons due to many-body effects.

Contribution

The study introduces a practical many-body Wannier functions approach to analyze charge fluctuations and excitonic states in a 1D Mott insulator, aligning theory with experimental observations.

Findings

Theoretical spectra qualitatively match experimental data.

Excitons, especially even-parity ones, are weakly bound by many-body effects.

The method effectively elucidates charge fluctuation roles in excited states.

Abstract

We have applied a many-body Wannier functions method to theoretically calculate an excitonic optical conductivity spectrum and energy structure in a one-dimensional (1D) Mott insulator at absolute zero temperature with large system size. Focusing on full charge fluctuations associated with pairs of a holon and doublon, we employ a charge model, which is interpreted as a good effective model to investigate photoexcitations of a 1D extended Hubbard model at half-filling in the spin-charge separation picture. As a result, the theoretical spectra with appropriate broadenings qualitatively reproduce the recent experimental data of ET-F$_{2}$TCNQ at 294 K with and without a modulated electric field. Regarding the excitonic energy structure, we have found that the excitons, especially for even-parity, are weakly bound by many-body effects. This is also consistent with the fitting parameters reported in the recent experiment. Thus, our theoretical method presented in this paper is practically useful to understand physical roles of charge fluctuations in many-body excited states of a 1D Mott insulator.