Disorder induced collapse of the electron phonon coupling in MgB${}_2$ observed by Raman Spectroscopy

Abstract

The Raman spectrum of the superconductor MgB${}_2$ has been measured as a function of the Tc 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 1.22 for films with T${}_c$ 39K and 0.80 for films with T${}_c\le$19K.

arXiv comment5 pages, 4 figures

References in corpus (24)

• Superconductivity of metallic boron in MgB_2
• Beyond Eliashberg superconductivity in MgB2: anharmonicity, two-phonon scattering, and multiple gaps
• Superconductivity of MgB2: Covalent Bonds Driven Metallic
• Thin Film Magnesium Boride Superconductor with Very High Critical Current Density and Enhanced Irreversibility Field
• Phonon dispersion and electron-phonon coupling in MgB_2 and AlB_2
• Giant anharmonicity and non-linear electron-phonon coupling in MgB${}_2$; A combined first-principles calculations and neutron scattering study
• First-Principles Calculation of the Superconducting Transition in MgB2 within the Anisotropic Eliashberg Formalism
• Two-gap superconductivity in MgB${}_2$: clean or dirty?
• Multiband model for tunneling in MgB2 junctions
• Electronic Structure, Electron-Phonon Coupling, and Multiband Effects in MgB2
• Evidence for Two Superconducting Gaps in $Mg{B}_2$
• Phonon Density-of-States in MgB2
• Effect of lattice strain and defects on the superconductivity of MgB2
• Electronic and structural properties of superconducting MgB${}_2$, CaSi${}_2$ and related compounds
• Raman spectrum and lattice parameters of MgB2 as a function of pressure
• The Superconducting Gap in MgB_2: Electronic Raman Scattering Measurements of Single Crystals
• High critical current densities in superconducting MgB2 thin films
• Effect of Al doping on the optical phonon spectrum in Mg(1-x)Al(x)B(2)
• Calculated elastic and electronic properties of MgB${}_2$ at high pressures
• Direct observation of nm-scale Mg- and B-oxide phases at grain boundaries in MgB2
• Phonons in MgB2 by Polarized Raman Scattering on Single Crystals
• Absence of a structural transition up to 40 Gpa in MgB2 and the relevance of magnesium non-stoichiometry
• Raman spectra of MgB2 at high pressure and topological electronic transition
• Growth of superconducting MgB2 thin films

Cited by in corpus (3)

• Prospects for Improving the Intrinsic and Extrinsic Properties of Magnesium Diboride Superconducting Strands
• Tuning topological disorder in MgB${}_2$
• A new class of photo-catalytic materials and a novel principle for efficient water splitting under infrared and visible light - MgB2 as unexpected example