Anomalously enhanced photoemission from the Dirac point and symmetry of   the self-energy variations for the surface states in Bi2Se3
  Accurate analysis of the photoemission intensity from the surface states of Bi2Se3 reveals two unusual features: spectral line asymmetry and anomalously enhanced photoemission from the Dirac point. The former indicates a certain symmetry of a scattering process, which results in strongly k\omega-dependent contribution to the imaginary part of the self-energy that changes sign while crossing both the dispersion curves and the energy of the Dirac point. The latter is hard to describe by one particle spectral function while a final state interference seems to be plausible explanation. 
A. A. Kordyuk, V. B. Zabolotnyy, D. V. Evtushinsky, T. K. Kim, B.   Buechner, I. V. Plyushchay, H. Berger, S. V. Borisenko
cond-mat.mes-hall cond-mat.other cond-mat.str-el