Andreev reflection spectroscopy evidence for multiple gaps in MgB2
Zhuang-Zhi Li, Hong-Jie Tao, Yi Xuan, Zhi-An Ren, Guang-Can Che, Bai-Ru Zhao
DOI 10.1103/PhysRevB.66.064513 · Physical Review B
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Abstract
Andreev reflection tunneling spectroscopy on MgB2/PtIr point contacts have systematically been investigated. By fitting tunneling conductance to Blonder-Tinkham-Klapwijk theory, s-wave superconducting gaps were obtained. The distribution of the obtained gaps unequivocally shows two groups: one centered at 9.8 meV and the other peaked at 2.8 meV with a gap ratio of 3.5. For two typical gaps Δ1=1.92 meV and Δ2=3.45 meV their temperature-dependent behavior display that Δ1(T) unambiguously persists to the bulk Tc, 39 K, and Δ2(T) closes at 33 K. The results support multigap scenarios; in addition our experiments yield a much higher value of the large gap than the previous reports and theoretical predictions, indicating there may exist even stronger electron-phonon coupling in MgB2.
Source-reported materials — not catalogue approval
| Formula | Reported Tc (K) | Pressure (GPa) | Type |
|---|---|---|---|
| MgB2 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 39 | Pressure not reported | unknown |
| MgB2 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 39 | Pressure not reported | unknown |
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