Probing Local Variations of Superconductivity on the Surface of Ba(Fe1-xCox)2As2 Single Crystals

Abstract

The spatially resolved electrical transport properties have been studied on the surface of optimally-doped superconducting Ba(Fe1-xCox)2As2 single crystal by using a four-probe scanning tunneling microscopy. While some non-uniform contrast appears near the edge of the cleaved crystal, the scanning electron microscopy (SEM) reveals mostly uniform contrast. For the regions that showed uniform SEM contrast, a sharp superconducting transition at TC = 22.1 K has been observed with a transition width (delta)Tc = 0.2 K. In the non-uniform contrast region, TC is found to vary between 19.6 and 22.2 K with (delta)Tc from 0.3 to 3.2 K. The wavelength dispersive x-ray spectroscopy reveals that Co concentration remains 7.72% in the uniform region, but changes between 7.38% and 7.62% in the non-uniform region. Thus the variations of superconductivity are associated with local compositional change.

18 pages, 5 figures

References in corpus (10)

• Superconductivity at 38 K in the iron arsenide (Ba1-xKx)Fe2As2
• Superconductivity at 43 K in Samarium-arsenide Oxides $SmFeAs{O}_{1-x}{F}_x$
• Superconductivity at 22 K in Co-doped BaFe2As2 Crystals
• Determination of the phase diagram of the electron doped superconductor Ba(Fe${}_{1-x}$Co${}_x$)${}_2$As${}_2$
• Scanning Tunneling Spectroscopy and Vortex Imaging in the Iron-Pnictide Superconductor BaFe${}_{1.8}$Co${}_{0.2}$As${}_2$
• Superconductivity in SrFe_(2-x)Co_xAs_2: Internal Doping of the Iron Arsenide Layers
• Spin susceptibility, phase diagram, and quantum criticality in the electron-doped high Tc Superconductor Ba[Fe(1-x)Co(x)]2As2
• Unconventional London penetration depth in Ba(Fe0.93Co0.07)2As2 single crystals
• Imaging nanoscale Fermi surface variations in an inhomogeneous superconductor
• Nanoscale superconducting gap variations, strong coupling signatures and lack of phase separation in optimally doped BaFe1.86Co0.14As2