title: Superconductor-to-insulator transition and transport properties of underdoped YBa2Cu3O(y) crystals.
abstract: The carrier-concentration-driven superconductor-to-insulator (SI) transition as well as transport properties in underdoped YBa2Cu3O(y) twinned crystals is studied. The SI transition takes place at y approximately 6.3, carrier concentration n(SI)H approximately 3x10(20) cm(-3), anisotropy rho(c)/rho(ab) approximately 10(3), and the threshold resistivity rho(SI)ab approximately 0.8 mOmega cm which corresponds to a critical sheet resistance h/4e2 approximately 6.5 kOmega per CuO2 bilayer. The evolution of a carrier, nH infiniti y - 6.2, is clearly observed in the underdoped region. The resistivity and Hall coefficient abruptly acquire strong temperature dependence at y approximately 6.5 indicating a radical change in the electronic state.
authors.affiliation: NTT Basic Research Laboratories, 3-1, Morinosato Wakamiya, Atsugi-shi Kanagawa 243-0198, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Semba
authors.forename: A
authors.initials: A
authors.lastname: Matsuda