On the dependence of the critical temperature on pressure in the bisoliton model of high temperature superconductors

Abstract

In the framework of the bisoliton model we have studied the critical temperature T _c, as a function of the pressure P and of the hole concentration δ for the high temperature superconductors YBa₂Cu₃O_x and (La_1-xM_x)₂CuO₄. Our results for δ ln T_c/δ ln V as a function of T _c describe quite satisfactorily the general trend of the experimental data. Furthermore we show that in the bisoliton model the energy gap δ (in units of Jg³/3, where J is the nearest-neighbour exchange integral and g is the nonlinearity parameter) is an universal function of δ/g. An analogous property is valid for T _c By fitting the maximum value of T _c we are able also to reproduce the experimental data for T _c(δ).