title: Critical point and the nature of the pseudogap of single-layered copper-oxide Bi2Sr2-xLaxCuO6+delta superconductors.
abstract: We apply strong magnetic fields of H=28.5 to 43 T to suppress superconductivity (SC) in the cuprates Bi2Sr2-xLaxCuO6+delta (x=0.65, 0.40, 0.25, 0.15, and 0), and investigate the low temperature (T) normal state by 63Cu nuclear spin-lattice relaxation rate (1/T1) measurements. We find that the pseudogap (PG) phase persists deep inside the overdoped region but terminates at x approximately 0.05, which corresponds to the hole doping concentration of approximately 0.21. Beyond this critical point, the normal state is a Fermi liquid that persists as the ground state when superconductivity is removed by the magnetic field. A comparison of the superconducting state with the H-induced normal state in the x=0.40 (Tc=32 K) sample indicates that there remains substantial part of the Fermi surface even in the fully developed PG state, which suggests that the PG and SC are coexisting matters.
authors.affiliation: Department of Physics, Okayama University, Okayama 700-8530, Japan.
authors.forename: Guo-Qing
authors.initials: GQ
authors.lastname: Zheng
authors.forename: P L
authors.initials: PL
authors.lastname: Kuhns
authors.forename: A P
authors.initials: AP
authors.lastname: Reyes
authors.forename: B
authors.initials: B
authors.lastname: Liang
authors.forename: C T
authors.initials: CT
authors.lastname: Lin