Photoemission Signatures of Photoinduced Carriers and Excitons in One-Dimensional Mott Insulators

TL;DR

This paper theoretically investigates photoemission spectra in one-dimensional Mott insulators, revealing how strong correlations and exciton formation uniquely influence spectral features compared to semiconductors.

Contribution

It introduces a detailed analysis of photoemission signatures of photoinduced carriers and excitons in strongly correlated 1D Mott insulators, highlighting the role of fractionalized excitations.

Findings

Spectra reflect spinon dispersion when carriers are unbound.

Exciton formation leads to in-gap replica features.

Spectral features depend on doublon-holon binding degree.

Abstract

We theoretically study photoemission spectra for photodoped one-dimensional Mott insulators that can host excitons, and show that their spectral characteristics differ qualitatively from those of photodoped semiconductors. In conventional semiconductors, photoemission spectra are well understood; free charge carriers generate spectral weight near the bottom of the conduction band, while the formation of excitons leads to replica features of the valence band appearing inside the band gap. In one-dimensional Mott insulators, on the other hand, strong correlations give rise to fractionalized elementary excitations-spinons, holons, and doublons-which fundamentally modify the photoemission response. We find that when photodoped carriers, i.e., doublons and holons, remain unbound, the photoemission spectrum directly reflects the dispersion of spinons, i.e., magnetic elementary excitations. In contrast, when a doublon and a holon form an excitonic bound state, replica structures of the lower Hubbard band emerge inside the Mott gap, carrying contributions from both spinon and holon excitations. Importantly, the distribution of the in-gap signal depends sensitively on the degree of doublon-holon binding. The origin of these spectral features is clarified through a combination of exact diagonalization and the slave-particle approach. These results indicate that photoemission from photoinduced carriers and excitons in strongly correlated electron systems can provide information on magnetic properties and carrier-binding properties.