Metallic behavior of lightly doped La2-xSrxCuO4 with a Fermi surface forming an arc.

Lightly doped La2-xSrxCuO4 in the so-called "insulating" spin-glass phase has been studied by angle-resolved photoemission spectroscopy. We have observed that a "quasiparticle" (QP) peak crosses the Fermi level in the node direction of the d-wave superconducting gap, forming an "arc" of Fermi surface, which explains the metallic behavior at high temperatures of the lightly doped materials. The QP spectral weight of the arc smoothly increases with hole doping, which we attribute to the n approximately x behavior of the carrier number in the underdoped and lightly doped regions.