ARPES study of lightly doped La2−xSrxCuO4

Lightly doped La2−xSrxCuO4 in the so-called “insulating” spin-glass phase has been studied by angle-resolved photoemission spectroscopy. A quasi-particle (QP) peak crossing the Fermi level has been observed in the node direction of the d-wave superconducting gap, forming an “arc” of Fermi surface consistent with the recently observed metallic transport behavior at high temperatures of lightly doped materials. The spectral weight of the nodal QP smoothly increases with hole doping, corresponding to the n∼x behavior of the carrier number in the underdoped and lightly doped regions.