Real-space characterization of tetragonal CuO epitaxial films

Yong Zhong,Yan-Feng Lv,Sha Han,Xu-Cun Ma,Can-Li Song,Qi-Kun Xue,Hang Yan,Ziyuan Dou,Rui-Feng Wang

doi:10.1063/5.0069356

Abstract

It is widely believed that the undoped Mott insulator is crucial to understand the origin of high-TC superconductivity and the complex phase diagram in cuprates. Tetragonal CuO, the simplest structure among cuprates, is regarded as an archetypal model to explore the ground state physics of Mott insulator. Here, we report on the epitaxial growth and surface characterization of tetragonal CuO thin film by combining ozone-assisted molecular beam epitaxy and multi-analytical techniques. In situ scanning tunneling microscopy measurement reveals two sets of Cu2+ square lattices with a reversed contrast of their apparent heights between neighboring domains. A spectroscopy study demonstrates an upper bound of the charge transfer gap as 3.68 eV, and quantitatively agrees with the previous photoemission and x-ray photoelectron results. Our work will deepen the understanding of high-energy electronic structures in parent cuprates.

Highlights

Zhang and Rice simplified it into an effective single-band model by considering the hybridization between Cu orbital and ligand O orbital,8 giving the same low-energy quasiparticle dispersion as the treatment of three-band model.9 The only deviation between the two pictures is the high-energy electronic structure
We report on the epitaxial growth and surface characterization of tetragonal CuO thin film by combining ozone-assisted molecular beam epitaxy and multi-analytical techniques
Angle-resolved photoemission spectroscopy (ARPES) and resonant inelastic x-ray scattering (RIXS) measurements display that Zhang–Rice singlet accounts quantitatively for the quasiparticle dispersion and magnon excitation in tetragonal CuO (T-CuO).11,12

Summary

Introduction

Zhang and Rice simplified it into an effective single-band model by considering the hybridization between Cu orbital and ligand O orbital,8 giving the same low-energy quasiparticle (namely, Zhang–Rice singlet) dispersion as the treatment of three-band model.9 The only deviation between the two pictures is the high-energy electronic structure. Tetragonal CuO, the simplest structure among cuprates, is regarded as an archetypal model to explore the ground state physics of Mott insulator.

Results

Conclusion