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Direct visualization of ambipolar Mott transition in cuprate CuO2 planes

Research paper by Yong Zhong, Ruifeng Wang, Xuefeng Zhang, Yuying Zhu, Ziyuan Dou, Yang Wang, Ding Zhang, Jing Zhu, Can-Li Song, Xu-Cun Ma, Qi-Kun Xue

Indexed on: 04 Sep '19Published on: 28 Apr '19Published in: arXiv - Physics - Superconductivity



Abstract

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 atomic-scale visualization of Mott insulator-metal transition in Sr1-xLaxCuO2+y cuprate films that cover the entire electron- and hole-doped regimes. Tunneling conductance measurements directly on the CuO2 planes reveal a systematic shift in the Fermi level, while the fundamental Mott-Hubbard band structure remains unchanged. Followed by the transition, low-lying electronic states are developed in the charge-transfer gap. The states exhibit a remarkable dichotomy between electron- and hole-doped cuprates and are associated with self-modulation doping of CuO2, similar to that in semiconductor heterostructures. The results form a basis for developing any microscopic theories for cuprate superconductivity.