The intrinsic electronic phase diagram of iron-oxypnictide superconductors

Abstract

We present the first comprehensive derivation of the intrinsic electronic phase diagram of the iron-oxypnictide superconductors in the normal state based on the analysis of the electrical resistivity ρ of both LaFeAsO1−xFx and SmFeAsO1−xFx for a wide range of doping. Our data give clear-cut evidence for unusual normal state properties in these new materials. In particular, the emergence of superconductivity at low doping levels is accompanied by distinct anomalous transport behavior in ρ of the normal state which is reminiscent of the spin density wave (SDW) signature in the parent material. At higher doping levels ρ of LaFeAsO1−xFx shows a clear transition from this pseudogap-like behavior to Fermi liquid-like behavior, mimicking the phase diagram of the cuprates. Moreover, our data reveal a correlation between the strength of the anomalous features and the stability of the superconducting phase. The pseudogap-like features become stronger in SmFeAsO1−xFx where superconductivity is enhanced and vanish when superconductivity is reduced in the doping region with Fermi liquid-like behavior.Polycrystalline LaFeAsO 1−x F x (0 ≤ x ≤ 0.2) and SmFeAsO 1−x F x (0 ≤ x ≤ 0.1) were prepared and characterized by powder X-ray diffraction (XRD) and wavelength-dispersive X-ray spectroscopy (WDX) [21] and further characterized by magnetization [22], nuclear mag-

Coexistence of static magnetism and superconductivity in SmFeAsO1−xFx as revealed by muon spin rotation

“…The comparison with the present SmFeAsO 1−x F x superconductors rather points towards an important role of low-energy spin fluctuations that emerge on doping away from an antiferromagnetic or SDW state. A recent work 30 has shown that the actual F content (as measured by energy dispersive X-ray analysis) of the SmFeAsO 1−x F x samples can be lower than the nominal one that is reported in our work. This would lead to a rescaling of the x axis of the phase diagram in our Fig.…”

Electronic and magnetic phase diagram of β-Fe1.01Se with superconductivity at 36.7 K under pressure

“…A T-linear resistivity is frequently taken as a fingerprint of a "noncanonical Fermi liquid system", as known for high T c cuprates [18] or in heavy Fermion metals [19,20]. This unusual linear temperature dependency of ρ(T) was also recently observed in the iron arsenides [21]. The temperature regime where we observe the linear resistivity is correlated to the region where NMR has detected the presence of increasing spin fluctuations in β-Fe 1.01 Se [13].…”

Spin density wave order and fluctuations inMn3Si: A transport study

“…The material LaFeAsO may be viewed as a representative case of the iron arsenide parent compounds exhibiting SDW order. Its magnetic transition occurs at T N = 137 K which is preceded by a structural transition from tetragonal to orthorhombic at T S = 160 K. 40,41 . The temperature dependence of the resistivity of this compound 42 is remarkably similar to that of Mn 3 Si.…”