title: Evidence for two superconducting gaps in MgB2.
abstract: We have measured the Raman spectra of polycrystalline MgB2 from 25 to 1200 cm(-1). A superconductivity-induced redistribution in the electronic Raman continuum was observed. Two pair-breaking peaks appear in the spectra, suggesting the presence of two superconducting gaps. The measured spectra were analyzed using a quasi-two-dimensional model in which two s-wave superconducting gaps open on two sheets of Fermi surface. For the gap values we have obtained Delta(1) = 22 cm(-1) ( 2.7 meV) and Delta(2) = 50 cm(-1) ( 6.2 meV). Our results suggest that a conventional phonon-mediated pairing mechanism occurs in the planar boron sigma bands and is responsible for the superconductivity of MgB2.
authors.affiliation: Department of Physics, Simon Fraser University, Burnaby, British Columbia, Canada V5A 1S6.
authors.forename: X K
authors.initials: XK
authors.lastname: Chen
authors.forename: M J
authors.initials: MJ
authors.lastname: Konstantinovic
authors.forename: J C
authors.initials: JC
authors.lastname: Irwin
authors.forename: D D
authors.initials: DD
authors.lastname: Lawrie
authors.forename: J P
authors.initials: JP
authors.lastname: Franck