Electronic structure ofLa2−xSrxCuO4in the vicinity of the superconductor-insulator transition

Abstract

We report on the result of angle-resolved photoemission study of ${\mathrm{La}}_{2\ensuremath{-}x}{\mathrm{Sr}}_{x}{\mathrm{CuO}}_{4}$ (LSCO) from an optimally doped superconductor $(x=0.15)$ to an antiferromagnetic insulator $(x=0).$ Near the superconductor-insulator transition $x\ensuremath{\sim}0.05,$ spectral weight is transferred with hole doping between two coexisting components, suggesting a microscopic inhomogeneity of the doped-hole distribution. For the underdoped LSCO $(x<~0.12),$ the dispersive band crossing the Fermi level becomes invisible in the $(0,0)\ensuremath{-}(\ensuremath{\pi},\ensuremath{\pi})$ direction unlike ${\mathrm{Bi}}_{2}{\mathrm{Sr}}_{2}{\mathrm{CaCu}}_{2}{\mathrm{O}}_{8+y}.$ These observations may be reconciled with the evolution of holes in the insulator into fluctuating stripes in the superconductor.