Evidence for competition between the superconducting and the pseudogap   state in (BiPb)_2(SrLa)_2CuO_{6+\delta} from muon-spin rotation experiments
  The in-plane magnetic penetration depth \lambda_{ab} in optimally doped (BiPb)_2(SrLa)_2CuO_{6+\delta} (OP Bi2201) was studied by means of muon-spin rotation. The measurements of \lambda_{ab}^{-2}(T) are inconsistent with a simple model of a d-wave order parameter and a uniform quasiparticle weight around the Fermi surface. The data are well described assuming the angular gap symmetry obtained in ARPES experiments [Phys. Rev. Lett {\bf 98}, 267004 (2007)], where it was shown that the superconducting gap in OP Bi2201 exists only in segments of the Fermi surface near the nodes. We find that the remaining parts of the Fermi surface, which are strongly affected by the pseudogap state, do not contribute significantly to the superconducting condensate. Our data provide evidence that high temperature superconductivity and pseudogap behavior in cuprates are competing phenomena. 
R. Khasanov, Takeshi Kondo, S. Str\"assle, D.O.G. Heron, A. Kaminski,   H. Keller, S.L. Lee, and Tsunehiro Takeuchi