Evidence for two-gap superconductivity in (Ba,K)Fe_2As_2 by directional point contact Andreev reflection spectroscopy

Abstract

Directional point-contact Andreev-reflection spectroscopy measurements on the Ba${}_{0.55}$K${}_{0.45}$Fe${}_2$As${}_2$ single crystals are presented. The spectra show significant differences when measured in the $ab$ plane in comparison with those measured in the $c$ direction of the crystal. In the latter case only a reduced point-contact conductance around zero bias has been revealed persisting well above $T_c$ and probably related to the structural and magnetic transitions in the system. Within the $ab$ plane two superconducting energy gaps are detected below $T_c$. Here a reduced conductance above $T_c$ could also be found. The fits of the $ab$-plane data to the superconducting s-wave two-gap model indicate that the smaller gap has a size below the BCS value while the large gap reveals much higher coupling strength.

published version

References in corpus (15)

• Superconductivity at 38 K in the iron arsenide (Ba1-xKx)Fe2As2
• Unconventional sign-reversing superconductivity in LaFeAsO_(1-x)F_x
• Spin density wave anomaly at 140 K in the ternary iron arsenide BaFe2As2
• Observation of Fermi-surface-dependent nodeless superconducting gaps in Ba0.6K0.4Fe2As2
• The superconductivity at 18 K in LiFeAs system
• Superconductivity in iron-based F-doped layered quaternary compound Nd[O1-xFx]FeAs
• Pressure induced superconductivity in CaFe${}_2$As${}_2$
• Evidence for two superconducting energy gaps in MgB2 by point-contact spectroscopy
• A minimal two-band model for the superconducting Fe-pnictides
• Anisotropic thermodynamic and transport properties of single crystalline (Ba${}_{1-x}$K${}_x$)Fe${}_2$As${}_2$ (x = 0 and 0.45)
• The BCS-like gap in superconductor SmFeAsO_0.85F_0.15
• Spin-singlet superconductivity with multiple gaps in PrO0.89F0.11FeAs
• Nodal Superconductivity with Multiple Gaps in SmFeAsO${}_{0.9}$F${}_{0.1}$
• Possible two-gap superconductivity in NdFeAs(O,F) probed by point-contact Andreev-reflection spectroscopy
• Point contact Andreev reflection spectroscopy of NdFeAsO_0.85

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