Magnetic penetration depth of Tl2Ba2CuO6+δ:Tc∼σ0 in the overdoped region

We report transverse-field muon-spin-rotation experiments carried out on Tl2Ba2CuO6+δ. This system spans the whole overdoped regime, andT c is reduced by excess oxygen doping, which increases the normal-state carrier concentration. In the heavily overdoped regimeσ(0) is found to scale linearly with the superconducting critical temperatureT c , similar to the behavior previously observed for other cuprates in the underdoped regime. However, for the overdoped region one has to explain the reduction ofσ0, thus the increase of the magnetic penetration depthλ, in spite of an increasing normal-state carrier concentration. We discuss some possible explanations for this behavior.