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

Abstract Anomalous suppression of T c has been found in an overdoped region of TlBa 2 Ca 2 Cu 3 O 9− δ superconductors. A heavily overdoped sample ( T c ≃100 K) was synthesized under high pressure. The T c was measured with decreasing the oxygen content until the sample becomes optimally doped state with a T c ≃131 K. A dip of T c was observed before the T c reaches to an optimal value i.e. in an overdoped region. This behavior is quite strange because T c is known to change monotonically in an overdoped region. Some possible explanations for this anomalous behavior will be presented.