Momentum-Resolved Visualization of Electronic Evolution in Doping a Mott Insulator

TL;DR

This study uses angle-resolved photoemission spectroscopy to directly visualize how the electronic structure of a Mott insulator evolves with electron doping, revealing the collapse of the Mott gap and emergence of low-energy states.

Contribution

It provides the first direct visualization of the Mott gap evolution and charge transfer dynamics in a doped cuprate using momentum-resolved spectroscopy.

Findings

The chemical potential jumps to the upper Hubbard band with slight doping.

The Mott gap rapidly collapses as doping increases.

Low-energy states emerge within the Mott gap region.

Abstract

High temperature superconductivity in cuprates arises from doping a parent Mott insulator by electrons or holes. A central issue is how the Mott gap evolves and the low-energy states emerge with doping. Here we report angle-resolved photoemission spectroscopy measurements on a cuprate parent compound by sequential in situ electron doping. The chemical potential jumps to the bottom of the upper Hubbard band upon a slight electron doping, making it possible to directly visualize the charge transfer band and the full Mott gap region. With increasing doping, the Mott gap rapidly collapses due to the spectral weight transfer from the charge transfer band to the gapped region and the induced low-energy states emerge in a wide energy range inside the Mott gap. These results provide key information on the electronic evolution in doping a Mott insulator and establish a basis for developing microscopic theories for cuprate superconductivity.