Doping-insensitive density-of-states suppression in polycrystalline iron-based superconductor

Abstract

We investigated the temperature dependence of the density-of-states in the iron-based superconductor SmO1−xFxFeAs (x = 0, 0.12, 0.15, 0.2) with high resolution angle-integrated photoemission spectroscopy. The density-of-states suppression is observed with decreasing temperature in all samples, revealing two characteristic energy scales (10 meV and 80 meV). However, no obvious doping dependence is observed. We argue that the 10 meV suppression is due to an anomalously dopingindependent normal state pseudogap, which becomes the superconducting gap once in the superconducting state; and alert the possibility that the 80 meV-scale suppression might be an artifact of the polycrystalline samples.

Violation of the Wiedemann-Franz law as evidence of the pseudogap in the iron-based superconductorBa(Fe1−xCoxMatusiak1, Wolf2 2015Phys. Rev. B11070View full textAdd to dashboardCite

“…These values are smaller than those deduced from the infrared spectroscopy, where ∆ PG = 87 meV [40], while they are similar to the results of time resolved, optical pump probe spectroscopy studies: ∆ PG = 52 -69 meV [41] and comparable to the widths resulting from the analysis of NMR data: ∆ PG = 42 -61 meV [42]. On the other hand, the relation between the width of the pseudogap and the SC critical temperature, which is 16 k B T c in Co4 and 17 k B T c for Co6, fits well in the range 9 -46 k B T c suggested for the "1111" iron-based superconductors [43], which in turn is also very similar to the 10 -40 k B T c range observed in the cuprate superconductor [44].…”

Variation in Electronic State of Ba(Fe1-xCox)2As2Alloy as Investigated in Terms of Transport Properties

“…In fact, such a feature is discernible in the photoemission spectra of related compounds RFeAsO (R is a rare-earth metal). 26,27) The reduction in Fermi surface area (carrier density) with decreasing T well explains the bad metallic behavior of as well as the increase in the magnitude of R H . Which scenario is more plausible for the present system is as yet unclear.…”

Scaling of the Temperature Dependent Resistivity in 11 Iron-Pnictide Superconductors

“…Our observation of a doping independent scaling law in the normal state of pnictide superconductors studied here is similar to that observed in cuprates [27], and recently in 1111 [35] and 122-iron-pnictide superconductor [38][39][40] could be probably used as indication that a gap-like feature is the reason for a predominant energy scale which controls the low energy excitations. The possible existence of a pseudogap in LaO 1−x F x FeAs and SmFeAsO 1−x F x 1111 pnictide compounds has been reported by Liu et al [45], Jia et al [46], and Ou et al [47] on the base of high resolution photoemission measurements. Two superconducting gaps (of about 12 meV on the two small hole-like and electron-like Fermi surface (FS) sheets, and 6 meV on the large hole-like FS) were observed by Ding et al [48] in the hole doped Ba 0.6 K 0.4 Fe 2 As 2 using a high-resolution angle-resolved photoelectron spectroscopy study.…”

“…Anyhow, the origin of the large gap values needs further experimental and theoretical studies [47]. Whether it can be caused by (i) local SDW fluctuation or (ii) CDW (charge density wave)/BOW (bond order wave) fluctuations supported by a strong enough electron-boson coupling and special intersite Coulomb interactions.…”