Evidence for an energy scale for quasiparticle dispersion in   Bi_2Sr_2CaCu_2O_8
  Quasiparticle dispersion in $Bi_{2}Sr_{2}CaCu_{2}O_{8}$ is investigated with improved angular resolution as a function of temperature and doping. Unlike the linear dispersion predicted by the band calculation, the data show a sharp break in dispersion at $50\pm10$ $meV$ binding energy where the velocity changes by a factor of two or more. This change provides an energy scale in the quasiparticle self-energy. This break in dispersion is evident at and away from the d-wave node line, but the magnitude of the dispersion change decreases with temperature and with increasing doping. 
P. V. Bogdanov, A. Lanzara, S. A. Kellar, X. J. Zhou, E. D. Lu, W.   Zheng, G. Gu, K. Kishio, J. -I. Shimoyama, Z. Hussain a...