Anomalous suppression of Tc in an overdoped region of TlBa2Ca2Cu3O9-δ

Anomalous suppression of Tc has been found in an overdoped region of TlBa2Ca2Cu3O9-δ superconductors. A heavily overdoped sample (Tc≅100 K) was synthesized under high pressure. The Tc was measured with decreasing the oxygen content until the sample becomes optimally doped state with a Tc≅131 K. A dip of Tc was observed before the Tc reaches to an optimal value i.e. in an overdoped region. This behavior is quite strange because Tc is known to change monotonically in an overdoped region. Some possible explanations for this anomalous behavior will be presented