465 research outputs found
The toy model for the high-Tc superconductivity
The simple microscopic model for the high-T_{C} superconductors based on the
electron-phonon (EPH) and electron-electron-phonon (EEPH) interactions has been
presented. On the {\it fold} mean-field level, it has been shown, that the
obtained model supplements the predictions based on the BCS van Hove scenario.
In particular: (i) For strong EEPH coupling and T<T_{C} the energy gap
(\Delta_{tot}) is very weak temperature dependent; up to the critical
temperature \Delta_{tot} extends into the anomalous normal state to the Nernst
temperature. (ii) The model explains well the experimental dependence of the
ratio R_{1}\equiv 2\Delta_{tot}^{(0)}/k_{B}T_{C} on doping for the reported
superconductors in the terms of the few fundamental parameters
Non-BCS temperature dependence of energy gap in thin film electron-doped cuprates
We investigate the dependence of the energy gap () on the temperature
() for the electron-doped high-temperature superconductors. The following
compounds, in the form of the thin films, have been taken into consideration:
(LCCO), (PCCO), and (NCCO). It was found that deviates from
the BCS prediction more, if a concentration of cerium assumes the lower values.
For the lowest concentration (in the case of LCCO and NCCO), the function
is not quite like the BCS curve, which is connected with the
existence of the residual Nernst region. Next, it has been pointed out that the
NCCO superconductor becomes structurally unstable for the maximum concentration
of cerium, which is leading to the anomalous dependence of the energy gap on
the temperature and the induction of the wide Nernst region
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