Disorder effects in pnictides : a tunneling spectroscopy study

Abstract

We present the synthesis and the tunneling spectroscopy study of superconducting FeSe0.5Te0.5 (Tc = 14 K), SmFeAsO0.85 (Tc = 45 K) and SmFeAsO0.9F0.1 (Tc = 52 K). The samples were characterized by Rietveld refinement of X-ray diffraction patterns and transport measurements. Tunneling experiments on FeSe0.5Te0.5 revealed a single superconducting gap of ~1 meV in BCS-like tunnelling conductance spectra. In SmFeAsO0.85 and SmFeAsO0.9F0.1 however, more complex spectra were observed characterized by two gap-like structures at ~4 meV and ~10 meV. These spectra are qualitatively understood assuming a two-band superconductor with a 's\pm' order parameter. We show that depending on the sign relation between the pairing amplitudes in the two bands, the interband quasiparticle scattering has a crucial effect on the shape of the tunneling spectra. Detailed analysis of the tunneling spectroscopy data supports the 's\pm' model, but single-gap spectra found in FeSe0.5Te0.5 are more compatible with a disorder-induced 's'-wave gap, due to the Se-Te substitution.

11 pages, 7 figures

References in corpus (31)

• Superconductivity at 22 K in Co-doped BaFe2As2 Crystals
• Superconductivity at 36 K in beta-Fe1.01Se with the compression of the interlayer separation under pressure
• Scanning tunneling spectroscopy of high-temperature superconductors
• Superconductivity at 27 K in tetragonal FeSe under high pressure
• Extreme Sensitivity of Superconductivity to Stoichiometry in FeSe (Fe1+dSe)
• Superconductivity close to magnetic instability in Fe(Se1-xTex)0.82
• Tellurium substitution effect on superconductivity of the alpha-phase Iron Selenide
• Pressure induced superconductivity in CaFe${}_2$As${}_2$
• Reply to Comment on "Unconventional s-wave superconductivity in Fe(Se,Te)"
• Superconductivity up to 29 K in SrFe2As2 and BaFe2As2 at high pressures
• Bulk Superconductivity at 14 K in Single Crystals of Fe1+yTexSe1-x
• Superconductivity in Co-doped LaFeAsO
• The BCS-like gap in superconductor SmFeAsO_0.85F_0.15
• Coexistence of static magnetism and superconductivity in SmFeAsO1-xFx as revealed by muon spin rotation
• Scanning Tunneling Spectroscopy and Vortex Imaging in the Iron-Pnictide Superconductor BaFe${}_{1.8}$Co${}_{0.2}$As${}_2$
• Spin Gap and Resonance at the Nesting Wavevector in Superconducting FeSe0.4Te0.6
• Momentum dependence of the superconducting gap in Ba${}_{1-x}$K${}_x$Fe${}_2$As${}_2$
• Superconductivity induced by cobalt doping in iron-based oxyarsenides
• Effect of Co doping on superconductivity and transport properties in SmFe${}_{1-x}$Co${}_x$AsO
• Superconductivity under high pressure in LaFeAsO
• Momentum-resolved superconducting gap in the bulk of Ba${}_{1-x}$K${}_x$Fe${}_2$As${}_2$ from combined ARPES and $\mu$SR measurements
• Coexistence of magnetic fluctuations and superconductivity in the pnictide high temperature superconductor SmFeAsO${}_{1-x}$F${}_x$ measured by muon spin rotation
• High temperature superconductivity (Tc onset at 34K) in the high pressure orthorhombic phase of FeSe
• Superconductivity in LaFeAs${}_{1-x}$P${}_x$O: effect of chemical pressures and bond covalency
• The Stoichiometry of FeSe
• Scanning tunneling spectroscopy of SmFeAsO0.85: Possible evidence for d-wave order parameter symmetry
• Nodal Superconductivity with Multiple Gaps in SmFeAsO${}_{0.9}$F${}_{0.1}$
• Scanning Tunneling Spectroscopy on the novel superconductor CaC6
• Pressure-induced superconductivity in Iron pnictide compound SrFe2As2
• Superconductivity in Co-doped SmFeAsO
• Local tunneling spectroscopy of the electron-doped cuprate Sm1.85Ce0.15CuO4

Cited by in corpus (13)

• Optical conductivity of Ba0.6 K0.4 Fe2 As2 : The effect of in-plane and out-of-plane doping in the superconducting gap
• Observing the origin of superconductivity in quantum critical metals
• Band hybridization induced odd-frequency pairing in multiband superconductors
• Tracing the $s_{\pm }$-symmetry in iron pnictides by controlled disorder
• Anomalous dependence of the c-axis polarized Fe B${}_{1g}$ phonon mode with Fe and Se concentrations in Fe${}_{1+y}$Te${}_{1-x}$Se${}_x$
• Microwave photon-assisted phase-incoherent Cooper-pair tunneling in a Josephson STM
• Evolution of Superconducting Gaps in Th-Substituted Sm${}_{1-x}$Th${}_x$OFeAs Studied by Multiple Andreev Reflection Spectroscopy
• Interband coupling and transport interband scattering in $s_{\pm }$ superconductors
• Point-contact study of ReFeAs(1-x)Fx (Re=La, Sm) superconducting films
• Evidence of a multiple boson emission in Sm${}_{1-x}$Th${}_x$OFeAs
• Plasma etching of superconducting Niobium tips for scanning tunneling microscopy
• Excess current in ferromagnet-superconductor structures with fully polarized triplet component
• Differential conductance of point contacts between an iron-based superconductor and a normal metal