Raman scattering from a superconductivity-induced bound state in MgB2.
It is shown that the sharp peak in the E(2g) Raman spectrum of superconducting MgB2 is due to a bound state caused by the electron-phonon coupling. Our theory explains why this peak appears only in the spectra with E(2g) symmetry and only in the sigma but not the pi bands. The properties of the bound state and the Raman spectrum are investigated, also in the presence of impurity scattering.
Zeyher
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Max-Planck-Institut für Festkörperforschung, Heisenbergstrasse 1, 70569 Stuttgart, Germany.