Photoemission of a doped Mott insulator: spectral weight transfer and qualitative Mott-Hubbard description

TL;DR

This study uses photoelectron spectroscopy to observe spectral weight transfer in doped TiOCl, revealing key signatures of strong electron correlations and Mott physics without metallic quasiparticles.

Contribution

It provides the first direct experimental evidence of spectral weight transfer in a doped Mott insulator consistent with Mott-Hubbard theory.

Findings

Spectral weight shifts from the lower Hubbard band to an additional peak upon doping.

No metallic quasiparticle peak observed, explained by one-particle effects.

Results align with atomic limit predictions for electron occupancy changes.

Abstract

The spectral weight evolution of the low-dimensional Mott insulator TiOCl upon alkali-metal dosing has been studied by photoelectron spectroscopy. We observe a spectral weight transfer between the lower Hubbard band and an additional peak upon electron-doping, in line with quantitative expectations in the atomic limit for changing the number of singly and doubly occupied sites. This observation is an unconditional hallmark of correlated bands and has not been reported before. In contrast, the absence of a metallic quasiparticle peak can be traced back to a simple one-particle effect.