Anomalously enhanced photoemission from the Dirac point and other peculiarities in the self-energy of the surface-state quasiparticles in Bi2Se3

Line-shape 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 can be described by the one-particle spectral function assuming that the self-energy has an energy-momentumdependent contribution to the imaginary part, which changes sign when crossing both the dispersion curves and the energy of the Dirac point. The anomalous enhancement can hardly be understood as a self-energy effect, while a final-state interference seems to be a more plausible explanation.