Disorder-induced collapse of the electron-phonon coupling inMgB2observed by Raman spectroscopy

2003/05/20 by K. A. Yates, Gavin Burnell, G. Burnell +7
Materials Science · Physics and Astronomy · #Physics of Superconductivity and Magnetism #Superconductivity in MgB2 and Alloys #Thermal Expansion and Ionic Conductivity #cond-mat.supr-con

paper · pdf · doi:10.1103/physrevb.68.220512

5 pages, 4 figures

arxiv created 2003/05/20 · openalex publication_date 2003/12/31 · arxiv updated 2009/11/30 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/28

Abstract

The Raman spectrum of the superconductor MgB₂ has been measured as a function of the T_c of the film. A striking correlation is observed between the T_c onset and the frequency of the E_2g mode. Analysis of the data with the McMillan formula provides clear experimental evidence for the collapse of the electron-phonon coupling at the temperature predicted for the convergence of two superconducting gaps into one observable gap. This gives indirect evidence of the convergence of the two gaps and direct evidence of a transition to an isotropic state at 19 K. The value of the electron-phonon coupling constant is found to be 1.19 for films with T_c\ensuremath≃39K and 0.80 for films with T_c<~19K.

Citations

• Effect of the Al content on the optical phonon spectrum inMg1−xAlxB2
• Superconductivity inMgB2: Clean or Dirty?
• Absence of a structural transition up to 40 GPa inMgB2and the relevance of magnesium nonstoichiometry
• Phonon Dispersion and Electron-Phonon Coupling inMgB2andAlB2
• Transition Temperature of Strong-Coupled Superconductors
• Raman spectrum and lattice parameters ofMgB2as a function of pressure