Overdoped Cuprate Superconductors Research Articles

Extended gapless regions in disordereddx2−y2wave superconductors

A generalization of the Abrikosov-Gorkov equations for non-magnetic impurities in unconventional superconductors is proposed, including higher harmonics in the expansion of the momentum dependent gap function and a momentum dependent impurity scattering potential. This model is treated within a self-consistent calculation to obtain the electronic density of states, the optical conductivity, and the gap function in a two-dimensional d_{x^2-y^2}-wave superconductor. It is argued that momentum dependent scattering from the impurities may lead to extended gapless regions in the gap function centered around the nodes of the pure d_{x^2-y^2}-wave superconductor. The associated enhancement of the residual density of states may be responsible for the rapid decrease of T_c and the increase of the London penetration depth with hole doping observed in overdoped cuprate superconductors.

Muon spin rotation studies of doping in high-Tc superconductors

We present muon-spin-rotation (μSR) studies on under- and overdoped cuprate superconductors. In underdoped La2−xSrxCuO4 and YBa2Cu3O6 + x we find evidence for a non-uniform magnetic state. The superconducting condensate density ns shows a characteristic dependence mainly on Tc and the doping state of the CuO2-planes. Nearly completed CuOchains provide an additional contribution to ns.