Local density of electronic states in MgB2 studied by low temperature STM and STS: direct evidence for a multiple-gap superconductor
✍ Scribed by M Xu; Z Xiao; Z Wang; Y Takano; T Hatano; K Sagisaka; M Kitahara; D Fujita
- Publisher
- Elsevier Science
- Year
- 2003
- Tongue
- English
- Weight
- 299 KB
- Volume
- 541
- Category
- Article
- ISSN
- 0039-6028
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✦ Synopsis
Scanning tunneling microscopy and spectroscopy (STM/STS) experiments on a high-density sintered MgB 2 surface were performed at 4.2 K, using a low temperature STM. The intrinsic superconducting density of states (DOS) was obtained in the tunneling spectra exhibiting the BCS-shaped characteristic with a metallic background. A double-gap structure, with the gap values of D L ¼ 9:5 meV and D S ¼ 4:0 meV, was clearly observed in the local tunneling spectra. These values give a BCS ratio (2D=k B T C ) of 5.6 and 2.4, respectively, well above and well below the BCS limit. The result supports the multiple-gap model in MgB 2 in the clean limit. The proximity effect observed in the conductance spectra and the origin of the varied reported energy gap values of MgB 2 were also discussed in this study.