Interplay Between Conventional Electron-Phonon Superconductivity and Density Waves in Two Dimensional Systems
The interplay between conventional BCS superconductivity and charge or spin density waves in two dimensional systems is analyzed using a model Hamiltonian. The model Hamiltonian, which includes both electron-phonon and electron-electron interactions, is solved by means of a unitary Bogoliubov transformation. The order parameters of the possible broken symmetries are obtained in the mean field approximation. It is found that, for a large range of the relevant interaction parameters entering into the problem, superconductivity and density waves can coexist if the Fermi level lies close to a one-electron bands saddle point. The implications of this coexistence to the high T c superconductors phenomenology is discussed.
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