Enhanced low-energy magnetic excitations evidencing the Cu-induced localization in an Fe-based superconductor Fe${}_{0.98}$Te${}_{0.5}$Se${}_{0.5}$

Abstract

We have performed inelastic neutron scattering measurements on optimally-doped Fe${}_{0.98}$Te${}_{0.5}$Se${}_{0.5}$ and 10% Cu-doped Fe${}_{0.88}$Cu${}_{0.1}$Te${}_{0.5}$Se${}_{0.5}$ to investigate the substitution effects on the spin excitations in the whole energy range up to 300 meV. It is found that substitution of Cu for Fe enhances the low-energy spin excitations ($\le$ 100 meV), especially around the (0.5, 0.5) point, and leaves the high-energy magnetic excitations intact. In contrast to the expectation that Cu with spin 1/2 will dilute the magnetic moments contributed by Fe with a larger spin, we find that the 10% Cu doping enlarges the effective fluctuating moment from 2.85 to 3.13 ${\mu }_{\mathrm{B}}$/Fe, although there is no long- or short-range magnetic order around (0.5, 0.5) and (0.5, 0). The presence of enhanced magnetic excitations in the 10% Cu doped sample which is in the insulating state indicates that the magnetic excitations must have some contributions from the local moments, reflecting the dual nature of the magnetism in iron-based superconductors. We attribute the substitution effects to the localization of the itinerant electrons induced by Cu dopants. These results also indicate that the Cu doping does not act as electron donor as in a rigid-band shift model, but more as scattering centers that localize the system.

Published in PRB, 8 pages, 3 figures

References in corpus (21)

• Magnetism and its microscopic origin in iron-based high-temperature superconductors
• Multiband magnetism and superconductivity in Fe-based compounds
• From (pi, 0) magnetic order to superconductivity with (pi, pi) magnetic resonance in Fe1.02(Te1-xSex)
• Spin Gap and Resonance at the Nesting Wavevector in Superconducting FeSe0.4Te0.6
• Where Are the Extra d Electrons in Transition-Metal Substituted Fe Pnictides?
• Nature of magnetic excitations in superconducting BaFe${}_{1.9}$Ni${}_{0.1}$As${}_2$
• Theory of the Magnetic Moment in Iron Pnictides
• Importance of Fermi surface topology for high temperature superconductivity in electron-doped iron arsenic superconductors
• Spin waves in the $(\pi ,0)$ magnetically ordered iron chalcogenide Fe${}_{1.05}$Te
• Metal - Insulator transition in Fe1.01-xCuxSe
• Electron-Hole Asymmetry in Superconductivity of Pnictides Originated from the Observed Rigid Chemical Potential Shift
• Inelastic neutron scattering study on the resonance mode in an optimally doped superconductor LaFeAsO${}_{0.92}$F${}_{0.08}$
• Neutron spectroscopy evidence on the dual nature of magnetic excitations in a van der Waals metallic ferromagnet Fe${}_{2.72}$GeTe${}_2$
• Soft striped magnetic fluctuations competing with superconductivity in Fe_{1+x}Te
• Theory of the evolution of magnetic order in Fe${}_{1+y}$Te compounds with increasing interstitial iron
• Magnetic order tuned by Cu substitution in Fe1.1-zCuzTe
• Strong similarities between the local electronic structure of insulating iron pnictide and lightly doped cuprate
• Local breaking of four-fold rotational symmetry by short-range magnetic order in heavily overdoped Ba(Fe${}_{1-x}$Cu${}_x$)${}_2$As${}_2$
• Substitution of Ni for Fe in superconducting Fe${}_{0.98}$Te${}_{0.5}$Se${}_{0.5}$ depresses the normal-state conductivity but not the magnetic spectral weight
• Toward the Mott state with Magnetic Cluster Formation in Heavily Cu-Doped NaFe${}_{1-x}$Cu${}_x$As
• Spin dynamics in NaFeAs and NaFe${}_{0.53}$Cu${}_{0.47}$As probed by resonant inelastic X-ray scattering

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