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? x Cu x As 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? x Cu x As 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- T c superconductivity.
展开▼
机译:铁基超导电性在反铁磁有序状态下发展,并脱离了有害金属的正常态,这被解释为起源于近似的莫特跃迁。在铁酸铁的相图中能否实现真正的莫特绝缘子仍然是一个悬而未决的问题。在这里,我们使用传输,透射电子显微镜,X射线吸收光谱,共振非弹性X射线散射和中子散射来证明NaFe 1? x≈0.5附近的x Cu> Cu x sub> As表现出真实的空间Fe和Cu有序性,并且是反铁磁绝缘体,其绝缘性能持续高于Néel温度,表明是Mott绝缘体。当x从0.5减小时,反铁磁有序矩连续减小,从而产生超导〜x = 0.05。我们在NaFe 1中发现了Mott绝缘状态? x sub> Cu x sub> As因此使其成为唯一已知的铁基材料,其中超导可以平稳地连接到Mott绝缘状态,从而突出了电子相关性在高温下的重要作用。 -T c sub>超导。
展开▼