1,052 research outputs found
Nonlinear Doping of Cuprate Superconductors -- The case of Bi_2Sr_{2-x}La_xCuO_{6+\delta}
We analyze the hole doping mechanism in Bi_2Sr_{2-x}La_xCuO_{6+\delta}
(BSLCO). The singular optimum around x=0.35 is found to be connected with a
feedback between the doped CuO_2 layers and its dopant reactant
[La^{3+}/Bi^{3+}-O_\delta] locking the number of doped holes preferentially on
to the universal optimum n_opt=0.16.Comment: Typos correcte
Quantum criticality and the phase diagram of the cuprates
I discuss a proposed phase diagram of the cuprate superconductors as a
function of temperature, carrier concentration, and a strong magnetic field
perpendicular to the layers. I show how the phase diagram gives a unified
interpretation of a number of recent experiments.Comment: 2 pages, 1 figure; Talk at M2S IX, Tokyo; (v2) corrected typo
Hall effect in the normal state of high Tc cuprates
We propose a model for explaining the dependence in temperature of the Hall
effect of high Tc cuprates in the normal state in various materials. They all
show common features: a decrease of the Hall coefficient RH with temperature
and a universal law, when plotting RH(T)/RH(T0) versus T/T0, where T0 is
defined from experimental results. This behaviour is explained by using the
well known electronic band structure of the CuO2 plane, showing saddle points
at the energies ES in the directions (0,+/-pi) and (+/-pi,0). We remark that in
a magnetic field, for energies E>ES the carrier orbits are hole-like and for
E<ES they are electron-like, giving opposite contributions to RH. We are abble
to fit the experimental results for a wide range of hole doping, and to fit the
universal curve. For us kb*T0 is simply EF-ES, where EF is the Fermi level
varying with the doping.Comment: 7 pages, 11 figure
Disorder, Metal-Insulator crossover and Phase diagram in high-Tc cuprates
We have studied the influence of disorder induced by electron irradiation on
the normal state resistivities of optimally and underdoped YBa2CuOx
single crystals, using pulsed magnetic fields up to 60T to completely restore
the normal state. We evidence that point defect disorder induces low T upturns
of rho(T) which saturate in some cases at low T in large applied fields as
would be expected for a Kondo-like magnetic response. Moreover the magnitude of
the upturns is related to the residual resistivity, that is to the
concentration of defects and/or their nanoscale morphology. These upturns are
found quantitatively identical to those reported in lower Tc cuprates, which
establishes the importance of disorder in these supposedly pure compounds. We
therefore propose a realistic phase diagram of the cuprates, including
disorder, in which the superconducting state might reach the antiferromagnetic
phase in the clean limit.Comment: version 2 with minor change
High-field Hall resistivity and magnetoresistance in electron-doped Pr_2-xCe_xCuO_{4-\delta}
We report resistivity and Hall effect measurements in electron-doped
PrCeCuO films in magnetic field up to 58 T. In
contrast to hole-doped cuprates, we find a surprising non-linear magnetic field
dependence of Hall resistivity at high field in the optimally doped and
overdoped films. We also observe a crossover from quadratic to linear field
dependence of the positive magnetoresistance in the overdoped films. A spin
density wave induced Fermi surface reconstruction model can be used to
qualitatively explain both the Hall effect and magnetoresistance.Comment: PRL in pres
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