title: Coexistence of Midgap Antiferromagnetic and Mott States in Undoped, Hole- and Electron-Doped Ambipolar Cuprates.
abstract: We report the first observation of the coexistence of a distinct midgap state and a Mott state in undoped and their evolution in electron and hole-doped ambipolar Y_{0.38}La_{0.62}(Ba_{0.82}La_{0.18})_{2}Cu_{3}O_{y} films using spectroscopic ellipsometry and x-ray absorption spectroscopies at the O K and Cu L_{3,2} edges. Supported by theoretical calculations, the midgap state is shown to originate from antiferromagnetic correlation. Surprisingly, while the magnetic state collapses and its correlation strength weakens with dopings, the Mott state in contrast moves toward a higher energy and its correlation strength increases. Our result provides important clues to the mechanism of electronic correlation strengths and superconductivity in cuprates.
authors.affiliation: Singapore Synchrotron Light Source, National University of Singapore, 5 Research Link, Singapore 117603, Singapore.|NUSSNI-NanoCore, National University of Singapore, Singapore 117576, Singapore.|Department of Physics, National University of Singapore, Singapore 117542, Singapore.|SZU-NUS Collaborative Innovation Center for Optoelectronic Science & Technology, Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Optoelectronic Engineering, Shenzhen University, Shenzhen 518060, China.
authors.forename: Xinmao
authors.initials: X
authors.lastname: Yin
authors.affiliation: NUSSNI-NanoCore, National University of Singapore, Singapore 117576, Singapore.|Department of Physics, National University of Singapore, Singapore 117542, Singapore.
authors.forename: Shengwei
authors.initials: S
authors.lastname: Zeng
authors.affiliation: Department of Physics, National University of Singapore, Singapore 117542, Singapore.|Centre for Advanced 2D Materials and Graphene Research Centre, National University of Singapore, Singapore 117546, Singapore.|Department of Physics, Indian Institute of Science, Bangalore 560012, India.
authors.forename: Tanmoy
authors.initials: T
authors.lastname: Das
authors.affiliation: The Institute of Mathematical Sciences, Chennai 600041, India.|Perimeter Institute for Theoretical Physics, Waterloo, Ontario N2L 2Y5, Canada.
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authors.initials: G
authors.lastname: Baskaran
authors.affiliation: Singapore Synchrotron Light Source, National University of Singapore, 5 Research Link, Singapore 117603, Singapore.|NUSSNI-NanoCore, National University of Singapore, Singapore 117576, Singapore.|Department of Physics, National University of Singapore, Singapore 117542, Singapore.
authors.forename: Teguh Citra
authors.initials: TC
authors.lastname: Asmara
authors.affiliation: Singapore Synchrotron Light Source, National University of Singapore, 5 Research Link, Singapore 117603, Singapore.|NUSSNI-NanoCore, National University of Singapore, Singapore 117576, Singapore.
authors.forename: Iman
authors.initials: I
authors.lastname: Santoso
authors.affiliation: Singapore Synchrotron Light Source, National University of Singapore, 5 Research Link, Singapore 117603, Singapore.
authors.forename: Xiaojiang
authors.initials: X
authors.lastname: Yu
authors.affiliation: Singapore Synchrotron Light Source, National University of Singapore, 5 Research Link, Singapore 117603, Singapore.
authors.forename: Caozheng
authors.initials: C
authors.lastname: Diao
authors.affiliation: Singapore Synchrotron Light Source, National University of Singapore, 5 Research Link, Singapore 117603, Singapore.
authors.forename: Ping
authors.initials: P
authors.lastname: Yang
authors.affiliation: Singapore Synchrotron Light Source, National University of Singapore, 5 Research Link, Singapore 117603, Singapore.|Department of Physics, National University of Singapore, Singapore 117542, Singapore.
authors.forename: Mark B H
authors.initials: MB
authors.lastname: Breese
authors.affiliation: NUSSNI-NanoCore, National University of Singapore, Singapore 117576, Singapore.|Department of Electrical and Computer Engineering, National University of Singapore, Singapore 117583, Singapore.
authors.forename: T
authors.initials: T
authors.lastname: Venkatesan
authors.affiliation: Department of Physics, National University of Singapore, Singapore 117542, Singapore.|Centre for Advanced 2D Materials and Graphene Research Centre, National University of Singapore, Singapore 117546, Singapore.
authors.forename: Hsin
authors.initials: H
authors.lastname: Lin
authors.affiliation: NUSSNI-NanoCore, National University of Singapore, Singapore 117576, Singapore.|Department of Physics, National University of Singapore, Singapore 117542, Singapore.
authors.lastname: Ariando
authors.affiliation: Singapore Synchrotron Light Source, National University of Singapore, 5 Research Link, Singapore 117603, Singapore.|NUSSNI-NanoCore, National University of Singapore, Singapore 117576, Singapore.|Department of Physics, National University of Singapore, Singapore 117542, Singapore.
authors.forename: Andrivo
authors.initials: A
authors.lastname: Rusydi