Charge-Density-Wave induced modifications to the quasiparticle   self-energy in 2H TaSe2
  The self-energy of the photo-hole in 2H-TaSe2 is measured by angle-resolved photoemission spectroscopy (ARPES) as a function of binding energy and temperature. In the charge-density wave (CDW) state, a structure in the self- energy is detected at ~ 65 meV that can not be explained by electron-phonon scattering. A reduction in the scattering rates below this energy indicates the collapse of a major scattering channel with the formation of the CDW state, accompanying the appearance of a bosonic "mode" in the excitation spectrum of the system. 
T. Valla, A. V. Fedorov, P. D. Johnson, J. Xue, K. E. Smith and F. J.   Di Salvo