  The electronic structure of the high-T_c superconductor Tl2Ba2CuO6+d is
studied by ARPES. For a very overdoped Tc=30K sample, the Fermi surface
consists of a single large hole pocket centered at (pi,pi) and is approaching a
topological transition. Although a superconducting gap with d_x^2-y^2 symmetry
is tentatively identified, the quasiparticle evolution with momentum and
binding energy exhibits a marked departure from the behavior observed in under
and optimally doped cuprates. The relevance of these findings to scattering,
many-body, and quantum-critical phenomena is discussed.
