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Abstract:
We present results for the pseudogap ground state and its doping evolution in single-layered copper-oxide Bi2Sr2-x La (x) CuO6+delta . We apply very high magnetic fields up to 44 T to remove the superconducting state and reveal the hidden low temperature (T) normal state. Through Cu-63-NMR Knight shift and spin-lattice relaxation rate measurements, we find that there remains a finite density of states (DOS) at the Fermi level in the zero-T limit when the superconductivity is removed, which indicates that the pseudogap ground state is a metallic state with a finite volume of Fermi surface. The residual DOS in the pseudogap ground state decreases with decreasing doping (increasing x), but remains quite large even at the vicinity of the magnetically ordered phase of xa parts per thousand yen 0.8. The result indicates that the superconductivity emerges from the remaining Fermi surface and coexists with the pseudogap.