Direct Visualization of Ambipolar Mott Transition in Cuprate CuO2 Planes

• DOI: 10.1103/physrevlett.125.077002
• Publication Date: 2020-08-12T21:39:26Z
• Authors: Yong Zhong; Jia-Qi Fan; Rui-Feng Wang; ShuZe Wang; Xuefeng Zhang; Yuying Zhu; Ziyuan Dou; Xue-Qing Yu; Yang Wang; Ding Zhang; Jing Zhu; Can-Li Song; Xu-Cun Ma; Qi-Kun Xue
• Keywords: Superconductivity (cond-mat.supr-con); Condensed Matter - Materials Science; Condensed Matter - Strongly Correlated Electrons; Strongly Correlated Electrons (cond-mat.str-el); Condensed Matter - Superconductivity; 0103 physical sciences; Materials Science (cond-mat.mtrl-sci); FOS: Physical sciences; 01 natural sciences

Identifying the essence of doped Mott insulators is one of the major outstanding problems in condensed matter physics and the key to understanding the high-temperature superconductivity in cuprates. We report real space visualization of Mott transition in Sr1-xLaxCuO2+y cuprate films that cover the entire electron- and hole-doped regimes. Tunneling conductance measurements directly on the cooper-oxide (CuO2) planes reveal a systematic shift in the Fermi level, while the fundamental Mott-Hubbard band structure remains unchanged. This is further demonstrated by exploring atomic-scale electronic response of CuO2 to substitutional dopants and intrinsic defects in a sister compound Sr0.92Nd0.08CuO2. The results could be better explained in the framework of self-modulation doping, similar to that in semiconductor heterostructures, and form a basis for developing any microscopic theories for cuprate superconductivity.<br/>5 pages, 4 figures, See Supplemental Material at https://journals.aps.org/prl/supplemental/10.1103/PhysRevLett.125.077002<br/>