Visualizing the evolution from the Mott insulator to a charge ordered insulator in lightly doped cuprates

TL;DR

This study uses scanning tunneling microscopy to explore how lightly doped cuprates transition from a Mott insulator to a charge ordered insulator, revealing the emergence of charge order before superconductivity.

Contribution

It provides the first direct visualization of the evolution from Mott insulator to charge ordered insulator in lightly doped cuprates using STM.

Findings

Doped charges transfer spectral weight to in-gap states.

A V-shaped suppression at the Fermi level appears with doping.

Checkerboard charge order emerges prior to superconductivity.

Abstract

A central question in the high temperature cuprate superconductors is the fate of the parent Mott insulator upon charge doping. Here we use scanning tunneling microscopy to investigate the local electronic structure of lightly doped cuprate in the antiferromagnetic insulating regime. We show that the doped charge induces a spectral weight transfer from the high energy Hubbard bands to the low energy in-gap states. With increasing doping, a V-shaped density of state suppression occurs at the Fermi level, which is accompanied by the emergence of checkerboard charge order. The new STM perspective revealed here is the cuprates first become a charge ordered insulator upon doping. Subsequently, with further doping, Fermi surface and high temperature superconductivity grow out of it.