J. L. González

A Theory for High-

We propose a general theory for the dependence of the critical and pseudogap temperatures T c and T* on the doping concentration for high-T c oxides, taking into account the charge inhomogeneities in the CuO 2 planes. Several recent experiments have revealed that the charge density p in a given compound (mostly underdoped) is intrinsic inhomogeneous with large spatial variations which leads to a local charge density p(r). These differences in the local charge concentration yield insulator and metallic regions, either in an intrinsic granular or in a stripe morphology. In the metallic region, the inhomogeneous charge density produces also spatial or local distributions which form Cooper pairs at a local superconducting critical temperatures T c (r) and zero temperature gap Δ 0 (r). For a given compound, the measured onset of the vanishing gap temperature is identified as the pseudogap temperature, that is, T*, which is the maximum of all T c (r). Below T*, due to the distribution of T c (r)s, there are some superconducting regions surrounded by an insulator or a metallic medium. The transition to a coherent superconducting state corresponds to the percolation threshold among the superconducting regions with different T c (r)s. The charge inhomogeneities have been studied by recent scanning tunneling microscopy experiments which provided a model for our phenomenological distribution. To make definite calculations and compare with the experimental results, we derive phase diagrams for the Bi 2 Sr 2 CaCu 2 O 8 + x (Bi2212), La 2 - x Sr x CuO 4 (LSCO), and YBa 2 Cu 3 O 7 - y (YBCO) families, with a mean field theory for superconductivity using an extended Hubbard Hamiltonian. We show also that this approach provides insights into several experimental features of high-T c oxides.

T_c

We report simultaneous hydrostatic pressure studies on the critical temperature

Superconductors Considering Inhomogeneous Charge Distribution

T_c

Pressure studies on the pseudogap and critical temperatures of a high-Tc superconductor

and on the pseudogap temperature

Upper critical field Hc2 calculations for the high critical temperature superconductors considering inhomogeneities

T^*

Transport critical current in granular samples under high magnetic fields

performed through resistivity measurements on an optimally doped high-

Pressure effects on the intergrain coupling in (Tl0.5Pb0.5)(Ba0.2Sr0.8)2Ca2Cu3Oy ceramic superconductor

T_c

Theory of the Diamagnetism Above the Critical Temperature for Cuprates

oxide

A novel percolation theory for high temperature superconductors

Hg_{0.82}Re_{0.18}Ba_2Ca_2Cu_3O_{8+\delta}

Measurements and analysis of the upper critical field H c 2 of underdoped and overdoped La 2 − x Sr x Cu O 4 series of compounds

. The resistivity is measured as function of the temperature for several different applied pressure below 1GPa. We find that both