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.

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

References in corpus (20)

• Superconductivity at 38 K in the iron arsenide (Ba1-xKx)Fe2As2
• 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 $(L{a}_{1-x}S{r}_x)OFeAs$
• Correlated electronic structure of LaOFeAs
• Funtional Renormalization Group Study of the Pairing Symmetry and Pairing Mechanism of the FeAs Based High Temperature 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${}_2$
• Superfluid density of the $\pm$s-wave state for the iron-based superconductors
• 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
• Antiferromagnetic Correlation and the Pairing Mechanism of the Cuprates and Iron Pnictides : a View From the Functional Renormalization Group Studies
• Scanning tunneling spectroscopic evidence for magnetic field-induced microscopic orders in the high-$T_c$ superconductor YBa${}_2$Cu${}_3$O${}_{7-\delta }$

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