Transport and magnetic properties are investigated for ${\mathrm{Tl}}_2$${\mathrm{Ba}}_2$${\mathrm{CuO}}_{6+\mathrm{\delta }}$, which shows a gradual transition from an 85-K superconductor to a nonsuperconducting normal metal, as the excess oxygen content δ is increased from ∼0 to ∼0.1. Hall measurements demonstrate that this transition arises from an overdoping of the hole carriers by excess oxygen. The temperature dependence of the resistivity is well fitted to a power-law dependence for all δ’s, while the exponent shows a systematic change from linear (δ∼0) to quadratic (δ∼0.1) dependence. No significant changes of the Hall coefficient nor spin susceptibility are observed at the superconductor-metal phase boundary, suggesting a similarity and continuity between both the electronic structures. This is in sharp contrast to the previous observations for ${\mathrm{La}}_{2\mathrm{-}\mathit{x}}$${\mathrm{Sr}}_{\mathit{x}}$${\mathrm{CuO}}_4$.

• Received 13 August 1990

DOI:https://doi.org/10.1103/PhysRevB.43.7875