CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES |
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Possible Nodeless Superconducting Gaps in Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ and YBa$_2$Cu$_3$O$_{7-x}$ Revealed by Cross-Sectional Scanning Tunneling Spectroscopy |
Ming-Qiang Ren1,2, Ya-Jun Yan1,2, Tong Zhang1,2**, Dong-Lai Feng1,2** |
1State Key Laboratory of Surface Physics, Department of Physics, and Advanced Materials Laboratory, Fudan University, Shanghai 200433
2Collaborative Innovation Center of Advanced Microstructures, Nanjing 210093 |
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Cite this article: |
Ming-Qiang Ren, Ya-Jun Yan, Tong Zhang et al 2016 Chin. Phys. Lett. 33 127402 |
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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 Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ (Bi2212) and YBa$_2$Cu$_3$O$_{7-x}$ (YBCO) along their $c$-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.
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Received: 08 November 2016
Published: 29 December 2016
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PACS: |
74.20.Rp
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(Pairing symmetries (other than s-wave))
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74.25.Jb
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(Electronic structure (photoemission, etc.))
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74.55.+v
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(Tunneling phenomena: single particle tunneling and STM)
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74.72.-h
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(Cuprate superconductors)
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Fund: Supported by the National Natural Science Foundation of China, and the National Key Research and Development Program of China under Grant No 2016YFA0300203. |
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