Zn-impurity effects on quasiparticle scattering in La2-xSrxCuO4 studied by angle-resolved photoemission spectroscopy

Angle-resolved photoemission measurements were performed on Zn-doped La2-xSrxCuO4 to investigate the effects of Zn impurities on the low-energy electronic structure. The Zn-impurity-induced increase in the quasiparticle width in momentum distribution curves (MDCs) is approximately isotropic on the entire Fermi surface and energy independent near the Fermi level (E-F). The increase in the MDC width is consistent with the increase in the residual resistivity due to the Zn impurities if we assume the carrier number to be 1-x for x=0.17 and the Zn impurity to be a potential scatterer close to the unitarity limit. For x=0.03, the residual resistivity is found to be higher than that expected from the MDC width, and the effects of antiferromagnetic fluctuations induced around the Zn impurities are discussed. The leading edges of the spectra near (pi,0) for x=0.17 are shifted toward higher energies relative to E-F with Zn substitution, indicating a reduction in the superconducting gap.