  It is predicted that electrons on the surface of a topological insulator can
acquire a mass (massive Dirac fermion) by opening up a gap at the Dirac point
when time-reversal symmetry is broken via the out-of-plane magnetization. We
report photoemission studies on a series of topological insulator materials
focusing on the spectral behavior in the vicinity of the Dirac node. Our
results show that the spectral intensity is suppressed resulting in a
"gap"-like feature in materials with or without any magnetic impurity or
doping. The Zeeman gap in magnetically doped samples, expected to be rather
small, is likely masked by the non-magnetic strong spectral weight suppression
involving a large energy scale we report. The photoemission spectral weight
suppression observed around the Dirac node thus cannot be taken as the sole
evidence for a time-reversal symmetry breaking magnetic gap. We discuss a few
possible extrinsic and kinematic origins of the Dirac point spectral weight
suppression ("gap") observed in many commonly studied topological materials.
