Collective modes in charge-density-wave superconductors
We investigate the coupling of the collective modes of a coexistent incommensurate charge-density-wave (CDW) superconductor (SC). We use a gauge-invariant random-phase approximation that correctly includes screening to treat both the amplitude and phase modes of the coupled system. Unlike previous work, the SC and CDW orderings are treated fully self-consistently, on an equal footing, and it is found that the only significant coupling is between the CDW and SC amplitude modes. We obtain qualitative agreement with Raman scattering data on NbSe2. The phase modes should not display any new structure in addition to that corresponding to pure CDW and pure superconducting order. © 1983 The American Physical Society.