title: A Mott insulator continuously connected to iron pnictide superconductors.
abstract: Iron-based superconductivity develops near an antiferromagnetic order and out of a bad-metal normal state, which has been interpreted as originating from a proximate Mott transition. Whether an actual Mott insulator can be realized in the phase diagram of the iron pnictides remains an open question. Here we use transport, transmission electron microscopy, X-ray absorption spectroscopy, resonant inelastic X-ray scattering and neutron scattering to demonstrate that NaFe1-xCuxAs near x≈0.5 exhibits real space Fe and Cu ordering, and are antiferromagnetic insulators with the insulating behaviour persisting above the Néel temperature, indicative of a Mott insulator. On decreasing x from 0.5, the antiferromagnetic-ordered moment continuously decreases, yielding to superconductivity ∼x=0.05. Our discovery of a Mott-insulating state in NaFe1-xCuxAs thus makes it the only known Fe-based material, in which superconductivity can be smoothly connected to the Mott-insulating state, highlighting the important role of electron correlations in the high-Tcsuperconductivity.
authors.affiliation: Department of Physics and Astronomy and Rice Center for Quantum Materials, Rice University, Houston, Texas 77005, USA.
authors.forename: Yu
authors.initials: Y
authors.lastname: Song
authors.affiliation: Canadian Neutron Beam Centre, Chalk River Laboratories, Chalk River, Ontario K0J 1J0, Canada.
authors.forename: Zahra
authors.initials: Z
authors.lastname: Yamani
authors.affiliation: Department of Physics and Astronomy and Rice Center for Quantum Materials, Rice University, Houston, Texas 77005, USA.|Department of Applied Physics, Northwestern Polytechnical University, Xian 710072, China.
authors.forename: Chongde
authors.initials: C
authors.lastname: Cao
authors.affiliation: Department of Physics and Astronomy and Rice Center for Quantum Materials, Rice University, Houston, Texas 77005, USA.
authors.forename: Yu
authors.initials: Y
authors.lastname: Li
authors.affiliation: Department of Physics and Astronomy and Rice Center for Quantum Materials, Rice University, Houston, Texas 77005, USA.
authors.forename: Chenglin
authors.initials: C
authors.lastname: Zhang
authors.affiliation: Department of Physics and Astronomy and Rice Center for Quantum Materials, Rice University, Houston, Texas 77005, USA.
authors.forename: Justin S
authors.initials: JS
authors.lastname: Chen
authors.affiliation: NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA.
authors.forename: Qingzhen
authors.initials: Q
authors.lastname: Huang
authors.affiliation: NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA.|Department of Materials Science and Engineering, University of Maryland, College Park, Maryland 20742-2115, USA.
authors.forename: Hui
authors.initials: H
authors.lastname: Wu
authors.affiliation: Department of Condensed Matter Physics and Materials Science, Brookhaven National National Laboratory, Upton, New York 11973, USA.
authors.forename: Jing
authors.initials: J
authors.lastname: Tao
authors.affiliation: Department of Condensed Matter Physics and Materials Science, Brookhaven National National Laboratory, Upton, New York 11973, USA.
authors.forename: Yimei
authors.initials: Y
authors.lastname: Zhu
authors.affiliation: Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
authors.forename: Wei
authors.initials: W
authors.lastname: Tian
authors.affiliation: Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
authors.forename: Songxue
authors.initials: S
authors.lastname: Chi
authors.affiliation: Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
authors.forename: Huibo
authors.initials: H
authors.lastname: Cao
authors.affiliation: Paul Scherrer Institute, Swiss Light Source, CH-5232 Villigen PSI, Switzerland.|Beijing National Laboratory for Condensed Matter Physics, and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China.
authors.forename: Yao-Bo
authors.initials: YB
authors.lastname: Huang
authors.affiliation: Paul Scherrer Institute, Swiss Light Source, CH-5232 Villigen PSI, Switzerland.
authors.forename: Marcus
authors.initials: M
authors.lastname: Dantz
authors.affiliation: Paul Scherrer Institute, Swiss Light Source, CH-5232 Villigen PSI, Switzerland.
authors.forename: Thorsten
authors.initials: T
authors.lastname: Schmitt
authors.affiliation: Department of Physics and Beijing Key Laboratory of Opto-electronic Functional Materials &Micro-nano Devices, Renmin University of China, Beijing 100872, China.|Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China.|Collaborative Innovation Center of Advanced Microstructures, Nanjing 210093, China.
authors.forename: Rong
authors.initials: R
authors.lastname: Yu
authors.affiliation: Department of Physics and Astronomy and Rice Center for Quantum Materials, Rice University, Houston, Texas 77005, USA.
authors.forename: Andriy H
authors.initials: AH
authors.lastname: Nevidomskyy
authors.affiliation: Department of Physics and Astronomy and Rice Center for Quantum Materials, Rice University, Houston, Texas 77005, USA.
authors.forename: Emilia
authors.initials: E
authors.lastname: Morosan
authors.affiliation: Department of Physics and Astronomy and Rice Center for Quantum Materials, Rice University, Houston, Texas 77005, USA.
authors.forename: Qimiao
authors.initials: Q
authors.lastname: Si
authors.affiliation: Department of Physics and Astronomy and Rice Center for Quantum Materials, Rice University, Houston, Texas 77005, USA.
authors.forename: Pengcheng
authors.identifier: 0000-0002-6088-3170
authors.initials: P
authors.lastname: Dai