We have measured the Raman spectra of polycrystalline MgB2 from 25 {\cm} to 1200 {\cm}. When the temperature was decreased below the superconducting transition temperature Tc, we observed a superconductivity-induced redistribution in the electronic Raman continuum. Two pair-breaking peaks appear in the spectra, suggesting the presence of two superconducting gaps. Furthermore, we have analyzed the measured spectra 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 Δ1=22cm−1 (2.7 meV) and Δ2=50cm−1 (6.2 meV). Our results suggest that a conventional phonon-mediated pairing mechanism occurs in the planar boron σ bands and is responsible for the superconductivity of MgB2.
@article{arxiv.cond-mat/0104005,
title = {Evidence for Two Superconducting Gaps in $MgB_2$},
author = {X. K. Chen and M. J. Konstantinovic and J. C. Irwin and D. D. Lawrie and J. P. Franck},
journal= {arXiv preprint arXiv:cond-mat/0104005},
year = {2016}
}