Measurement of a Sign-Changing Two-Gap Superconducting Phase in Electron-Doped Ba(Fe_{1-x}Co_x)_2As_2 Single Crystals using Scanning Tunneling Spectroscopy

Abstract

Scanning tunneling spectroscopic studies of $Ba(F{e}_{1-x}C{o}_x{)}_{2}A{s}_2$ (x = 0.06, 0.12) single crystals reveal direct evidence for predominantly two-gap superconductivity. These gaps decrease with increasing temperature and vanish above the superconducting transition $T_c$. The two-gap nature and the slightly doping- and energy-dependent quasiparticle scattering interferences near the wave-vectors $(\pm \pi ,0)$ and $(0,\pm \pi )$ are consistent with sign-changing $s$-wave superconductivity. The excess zero-bias conductance and the large gap-to-$T_c$ ratios suggest dominant unitary impurity scattering.

arXiv comment4 pages, 4 figures. Paper accepted for publication in Physical Review Letters. Contact author: Nai-Chang Yeh ([email protected])

References in corpus (35)

• Superconductivity at 38 K in the iron arsenide (Ba1-xKx)Fe2As2
• Unconventional sign-reversing superconductivity in LaFeAsO_(1-x)F_x
• Magnetic Order versus superconductivity in the Iron-based layered La(O1-xFx)FeAs systems
• Superconductivity at 43 K in Samarium-arsenide Oxides $SmFeAs{O}_{1-x}{F}_x$
• LaFeAsO${}_{1-x}$F${}_x$: A low carrier density superconductor near itinerant magnetism
• Superconductivity at 22 K in Co-doped BaFe2As2 Crystals
• Observation of Fermi-surface-dependent nodeless superconducting gaps in Ba0.6K0.4Fe2As2
• Superconductivity up to 37 K in (A1-xSrx)Fe2As2 with A=K and Cs
• Superconductivity and Phase Diagram in the Iron-based Arsenic-oxides ReFeAsO1-delta (Re = rare earth metal) without F-Doping
• Superconductivity at 25 K in hole doped $(L{a}_{1-x}S{r}_x)OFeAs$
• Reply to Comment on "Unconventional s-wave superconductivity in Fe(Se,Te)"
• Correlated electronic structure of LaOFeAs
• Funtional Renormalization Group Study of the Pairing Symmetry and Pairing Mechanism of the FeAs Based High Temperature Superconductors
• A Numerical Renormalization Group Study of the Superconducting and Spin Density Wave Instabilities in MFeAsO${}_{1-x}$F${}_x$ Compounds
• Fermi surface nesting induced strong pairing in iron-based superconductors
• The BCS-like gap in superconductor SmFeAsO_0.85F_0.15
• Multiband magnetism and superconductivity in Fe-based compounds
• Electronic structure of the iron-based superconductor LaOFeP
• Scanning Tunneling Spectroscopy and Vortex Imaging in the Iron-Pnictide Superconductor BaFe${}_{1.8}$Co${}_{0.2}$As${}_2$
• Role of multiband effects and electron-hole asymmetry in the superconductivity and normal state properties of Ba(Fe${}_{1-x}$Co${}_x$)${}_2$As${}_2$
• Flux dynamics and vortex phase diagram in $Ba(F{e}_{1-x}C{o}_x{)}_{2}A{s}_2$ single crystals revealed by magnetization and its relaxation
• Superfluid density of the $\pm$s-wave state for the iron-based superconductors
• Resonant impurity scattering in the $\pm$s-gap state of the Fe-based superconductors
• Integer and half-integer flux-quantum transitions in a niobium/iron-pnictide loop
• Point-Contact Spectroscopy of Iron-Based Layered Superconductor LaO${}_{0.9}$F${}_{0.1-\delta }$FeAs
• The cleavage surface of the BaFe_(2-x)Co_(x)As_(2) and Fe_(y)Se_(1-x)Te_(x) superconductors: from diversity to simplicity
• Local density of states and superconducting gap in the iron chalcogenide superconductor Fe${}_{1+\delta }$Se${}_{1-x}$Te${}_x$ observed by scanning tunneling spectroscopy
• Antiferromagnetic Correlation and the Pairing Mechanism of the Cuprates and Iron Pnictides : a View From the Functional Renormalization Group Studies
• Quasiparticle Scattering Interference in Superconducting Iron-pnictides
• Muon spin rotation study of magnetism and superconductivity in BaFe2-xCoxAs2 and Pr1-xSrxFeAsO
• Local quasiparticle density of states of superconducting SmFeAsO$1-x$F$x$ single crystals: Evidence for spin-mediated pairing
• Scanning tunneling spectroscopic evidence for magnetic field-induced microscopic orders in the high-$T_c$ superconductor YBa${}_2$Cu${}_3$O${}_{7-\delta }$
• Vortex as a probe - suggested measurement of the order parameter structure in iron-based superconductors
• Unconventional Low-Energy Excitations of Cuprate Superconductors
• Spectroscopic Evidence for Competing Order-Induced Pseudogap Phenomena and Unconventional Low-Energy Excitations in High-TC Cuprate Superconductors

Cited by in corpus (37)

• Unconventional Superconductivity
• Spectroscopic scanning tunneling microscopy insights into Fe-based superconductors
• Role of the orbital degree of freedom in iron-based superconductors
• A review of two-band superconductivity: materials and effects on the thermodynamic and reversible mixed-state properties
• Crossover from weak to strong pairing in unconventional superconductors
• Ginzburg-Landau theory for multiband superconductors: microscopic derivation
• Strong Correlations, Strong Coupling and s-wave Superconductivity in Hole-doped BaFe2As2 Single Crystals
• Evidence of a spin resonance mode in the iron-based superconductor Ba${}_{0.6}$K${}_{0.4}$Fe${}_2$As${}_2$ from scanning tunneling spectroscopy
• Optical conductivity of Ba0.6 K0.4 Fe2 As2 : The effect of in-plane and out-of-plane doping in the superconducting gap
• Conditions for non-monotonic vortex interaction in two-band superconductors
• Pseudogap in underdoped Ba${}_{1-x}$K${}_x$Fe${}_2$As${}_2$ as seen via optical conductivity
• Local inhomogeneity and filamentary superconductivity in Pr-doped CaFe${}_2$As${}_2$
• Unexpected weak spatial variation of local density of sates induced by individual Co impurity atoms in Na(Fe{1-x}Cox)As as revealed by scanning tunneling spectroscopy
• Surface terminations and layer-resolved spectroscopy in 122 iron pnictide superconductors
• Metastable $\pi$-junction between an s${}_{\pm }$-wave and an s-wave superconductor
• Zn-impurity effect and interplay of $s_{\pm }$- and $s_{++}$-pairings in Fe-based superconductors
• Improving quantum-transition temperatures in BaFe2As2-based crystals by removing local-lattice strain & electronic-structure disorder
• Planar hybrid superconductor-normal metal-superconductor thin film junctions based on BaFe1.8Co0.2As2
• Effect of surface morphology and magnetic impurities on the electronic structure in cobalt-doped BaFe2As2 superconductors
• Phase diagram of doped BaFe${}_2$As${}_2$ superconductor under broken $C_4$ symmetry
• Evidence for conventional superconductivity in SrPd2Ge2
• Coexistence of Clean- and Dirty-limit Superconductivity in LiFeAs
• Fluctuations in superconducting rings with two order parameters
• Superconducting gap symmetry in BaFe${}_{1.9}$Ni${}_{0.1}$As${}_2$ superconductor
• Transmittance and reflectance measurements at terahertz frequencies on a superconducting BaFe_{1.84}Co_{0.16}As_2 ultrathin film: an analysis of the optical gaps in the Co-doped BaFe_2As_2 pnictide
• Quasiparticle Interference in Fe-based Superconductors Based on a Five-Orbital Tight-Binding Model
• Interrogating the superconductor Ca10(Pt4As8)(Fe2-xPtxAs2)5 Layer-by-layer
• Electronic specific heat in BaFe${}_{2-x}$Ni${}_x$As${}_2$
• Testing the sign-changing superconducting gap in iron-based superconductors with quasiparticle interference and neutron scattering
• Surface reconstruction and charge modulation in BaFe2As2 superconducting film
• Effect of transition-metal substitution in iron-based superconductors
• Calculation of the effect of random superfluid density on the temperature dependence of the penetration depth
• Scanning Tunneling Spectroscopy on SrFe${}_2$(As${}_{1-\mathrm{x}}$P${}_{\mathrm{x}}$)${}_2$
• Enhanced Surface Superconductivity in Ba(Fe${}_{0.95}$Co${}_{0.05}$)${}_2$As${}_2$
• Superconducting Gap and Symmetry in FeSe_1-x_Te_x_ Studied by Specific Heat in Magnetic Fields
• Comparative studies of the scanning tunneling spectra in cuprate and iron-arsenide superconductors
• Crossover of the pairing symmetry from $s$- to $d$-wave in iron pnictide superconductors