Effect of Iodine Doping on Bi2_{2}Sr2_{2}Ca1_{1}Cu2_{2}Ox_{x}: Charge Transfer or Interlayer Coupling?

A comparative study has been made of iodine-intercalated Bi$_{2}$Sr$_{2}$Ca$_{1}$Cu$_{2}$O$_{x}$ single crystal and 1 atm O$_{2}$ annealed Bi$_{2}$Sr$_{2}$Ca$_{1}$Cu$_{1}$O$_{x}$ single crystal using AC susceptibility measurement, X-ray photoemission (XPS) and angle-resolved ultraviolet photoemission spectroscopy (ARUPS). AC susceptibility measurement indicates that O$_{2}$-doped samples studied have T$_{c}$ of 84 $^{o}$K, whereas T$_{c}$ of Iodine-doped samples studied are 80 $^{o}$K. XPS Cu 2p core level data establish that the hole concentration in the CuO$_{2}$ planes are essentially the same for these two kinds of samples. ARUPS measurements show that electronic structure of the normal states near the Fermi level has been strongly affected by iodine intercalation. We conclude that the dominant effect of iodine doping is to alter the interlayer coupling.Comment: LBL 9 pages, APS_Revtex. 5 Figures, available upon request. UW-Madison preprin

Interplay among critical temperature, hole content, and pressure in the cuprate superconductors

Within a BCS-type mean-field approach to the extended Hubbard model, a nontrivial dependence of T_c on the hole content per unit CuO_2 is recovered, in good agreement with the celebrated non-monotonic universal behaviour at normal pressure. Evaluation of T_c at higher pressures is then made possible by the introduction of an explicit dependence of the tight-binding band and of the carrier concentration on pressure P. Comparison with the known experimental data for underdoped Bi2212 allows to single out an `intrinsic' contribution to d T_c / d P from that due to the carrier concentration, and provides a remarkable estimate of the dependence of the inter-site coupling strength on the lattice scale.Comment: REVTeX 8 pages, including 5 embedded PostScript figures; other required macros included; to be published in Phys. Rev. B (vol. 54