A Mott insulator continuously connected to iron pnictide superconductors


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.

NEWS 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/
Journal article

Song, Yu, Yamani, Zahra, Cao, Chongde, et al.. "A Mott insulator continuously connected to iron pnictide superconductors." Nature Communications, 7, (2016) Springer Nature: http://dx.doi.org/10.1038/ncomms13879.

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