Song, YuYamani, ZahraCao, ChongdeLi, YuZhang, ChenglinChen, Justin S.Huang, QingzhenWu, HuiTao, JingZhu, YimeiTian, WeiChi, SongxueCao, HuiboHuang, Yao-BoDantz, MarcusSchmitt, ThorstenYu, RongNevidomskyy, Andriy H.Morosan, EmiliaSi, QimiaoDai, Pengcheng2017-01-092017-01-092016Song, Yu, Yamani, Zahra, Cao, Chongde, et al.. "A Mott insulator continuously connected to iron pnictide superconductors." <i>Nature Communications,</i> 7, (2016) Springer Nature: http://dx.doi.org/10.1038/ncomms13879.https://hdl.handle.net/1911/93742NEWS COVERAGE: A news release based on this journal publication is available online: http://news.rice.edu/2016/12/19/copper-stripes-help-iron-pnictide-lock-in-insulating-state/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-Tc superconductivity.engThis work is licensed under a Creative Commons Attribution 4.0 International License. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in the credit line; if the material is not included under the Creative Commons license, users will need to obtain permission from the license holder to reproduce the material. Journal articlehttp://dx.doi.org/10.1038/ncomms13879