Phase diagram and neutron spin resonance of superconducting NaFe${}_{1-x}$Cu${}_x$As

Abstract

We use transport and neutron scattering to study the electronic phase diagram and spin excitations of NaFe${}_{1-x}$Cu${}_x$As single crystals. Similar to Co- and Ni-doped NaFeAs, a bulk superconducting phase appears near $x\approx 2\%$ with the suppression of stripe-type magnetic order in NaFeAs. Upon further increasing Cu concentration the system becomes insulating, culminating in an antiferromagnetically ordered insulating phase near $x\approx 50\%$. Using transport measurements, we demonstrate that the resistivity in NaFe${}_{1-x}$Cu${}_x$As exhibits non-Fermi-liquid behavior near $x\approx 1.8\%$. Our inelastic neutron scattering experiments reveal a single neutron spin resonance mode exhibiting weak dispersion along $c$-axis in NaFe${}_{0.98}$Cu${}_{0.02}$As. The resonance is high in energy relative to the superconducting transition temperature $T_{\mathrm{c}}$ but weak in intensity, likely resulting from impurity effects. These results are similar to other iron pnictides superconductors despite the superconducting phase in NaFe${}_{1-x}$Cu${}_x$As is continuously connected to an antiferromagnetically ordered insulating phase near $x\approx 50\%$ with significant electronic correlations. Therefore, electron correlations is an important ingredient of superconductivity in NaFe${}_{1-x}$Cu${}_x$As and other iron pnictides.

arXiv commentaccepted for publication in PRB

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Cited by in corpus (8)

• Electron and Superconducting Properties of the AFeAs (A= Li, Na) Family Alkali-Metal Pnictides: Current Stage of the Research (mini-review)
• Doping effects of Cr on the physical properties of BaFe${}_{1.9-x}$Ni${}_{0.1}$Cr${}_x$As${}_2$
• Local breaking of four-fold rotational symmetry by short-range magnetic order in heavily overdoped Ba(Fe${}_{1-x}$Cu${}_x$)${}_2$As${}_2$
• Orbital-selective coherence-incoherence crossover and metal-insulator transition in Cu-doped NaFeAs
• RKKY coupled local moment magnetism in NaFe${}_{1-x}$Cu${}_x$As
• Fluctuating magnetism of Co- and Cu-doped NaFeAs
• Raman scattering study of NaFe${}_{0.53}$Cu${}_{0.47}$As
• Quasi-one-dimensional spin excitations in the iron pnictide NaFe${}_{0.53}$Cu${}_{0.47}$As