Enhanced low-energy magnetic excitations via suppression of the itinerancy in Fe0.98-zCuzTe0.5Se0.5

Abstract

We have performed resistivity and inelastic neutron scattering measurements on three samples of Fe0.98-zCuzTe0.5Se0.5 with z = 0, 0.02, and 0.1. It is found that with increasing Cu doping the sample's resistivity deviates progressively from that of a metal. However, in contrast to expectations that replacing Fe with Cu would suppress the magnetic correlations, the low-energy (no larger than 12 meV) magnetic scattering is enhanced in strength, with greater spectral weight and longer dynamical spin-spin correlation lengths. Such enhancements can be a consequence of either enlarged local moments or a slowing down of the spin fluctuations. In either case, the localization of the conduction states induced by the Cu doping should play a critical role. Our results are not applicable to models that treat 3d transition metal dopants simply as effective electron donors.

5 pages, 5 figures. To appear in PRB

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• Antiferromagnetic order and spin dynamics in iron-based superconductors
• Spin fluctuations in iron pnictides and chalcogenides: From antiferromagnetism to superconductivity
• Spin liquid polymorphism in a correlated electron system on the threshold of superconductivity
• Magnetism and superconductivity in Fe${}_{1+y}$Te${}_{1-x}$Se${}_x$
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• Enhanced low-energy magnetic excitations evidencing the Cu-induced localization in an Fe-based superconductor Fe${}_{0.98}$Te${}_{0.5}$Se${}_{0.5}$