APS -APS March Meeting 2017 - Event - A Mott insulator continuously connected to iron pnictide superconductors

摘要

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, andneutron scattering to demonstrate that NaFe$_{1-x}$Cu$_x$As near $xapprox 0.5$exhibits real space Fe and Cu ordering, andare antiferromagnetic insulators with the insulatingbehavior persisting above theN'eel temperature, indicative of a Mott insulator.Upon decreasing $x$ from $0.5$, the antiferromagnetic ordered moment continuously decreases, yielding to superconductivity around $x=0.05$.Our discovery of a Mott insulating state in NaFe$_{1-x}$Cu$_x$As thus makes it the only known Fe-based material in which superconductivity can be smoothlyconnected to the Mott insulating state,highlighting the important role of electron correlations in the high-$T_{m c}$ superconductivity.