MAGNETIC PENETRATION DEPTH OF TL2BA2CUO6+DELTA-TC-INFINITY-SIGMA-O IN THE OVERDOPED REGION

We report transverse-field muon-spin-rotation experiments carried out on T12Ba2CuO6+delta. This system spans the whole overdoped regime, and T(c) is reduced by excess oxygen doping, which increases the normal-state carrier concentration. In the heavily overdoped regime sigma(0) is found to scale linearly with the superconducting critical temperature T(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 of sigma0, thus the increase of the magnetic penetration depth lambda, in spite of an increasing normal-state carrier concentration. We discuss some possible explanations for this behavior.