Implications of Reflectance Measurements on the Mechanism for Superconductivity in MgB2
F. Marsiglio
DOI 10.1103/PhysRevLett.87.247001 · Physical Review Letters
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Abstract
Recent optical studies in c-axis oriented superconducting MgB2 films indicate that the electron-phonon coupling is weak. We reinforce this conclusion by examining the raw reflectance data; its frequency dependence is incompatible with strong electron-phonon scattering. This is further strengthened by analysis of the real part of the conductivity, and by the temperature dependence of the effective Drude scattering rate. Using a realistic electron-phonon spectral shape, we find λtr≈0.15. To the extent that λtr≈λ, this disagrees sharply with model calculations, and is far too low to provide the means for Tc=39K. A simple model is constructed with coupling to a high frequency excitation, which is consistent with both the low frequency optical data and the high Tc.
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 |
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