Fermi surface and quasiparticle excitations of overdoped Tl₂Ba₂CuO_6+d

The high- superconductor Tl2⁢Ba2⁢CuO6+ is studied by angle-resolved photoemission spectroscopy. For a very overdoped =30  K sample, the Fermi surface consists of a single large hole pocket centered at ( , ) and is approaching a topological transition. Although a superconducting gap with 2− 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.