Possible Nodeless Superconducting Gaps in BiSrCaCuO and YBaCuO Revealed by Cross-Sectional Scanning Tunneling Spectroscopy
arXiv:1611.04220 · doi:10.1088/0256-307X/33/12/127402
Abstract
Pairing in the cuprate high-temperature superconductors and its origin remain among the most enduring mysteries in condensed matter physics. With cross-sectional scanning tunneling microscopy/ spectroscopy, we clearly reveal the spatial-dependence or inhomogeneity of the superconducting gap structure of BiSrCaCuO (Bi2212) and YBaCuO (YBCO) along their -axes on a scale shorter than the interlayer spacing. By tunneling into the (100) plane of a Bi2212 single crystal and a YBCO film, we observe both U-shaped tunneling spectra with extended flat zero-conductance bottoms, and V-shaped gap structures, in different regions of each sample. On the YBCO film, tunneling into a (110) surface only reveals a U-shaped gap without any zero-bias peak. Our analysis suggests that the U-shaped gap is likely a nodeless superconducting gap. The V-shaped gap has a very small amplitude, and is likely proximity-induced by regions having the larger U-shaped gap.
arXiv comment6 pages, 5 figures
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