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

In the framework of the bisoliton model we have studied the critical temperature Tc as a function of the pressure P and of the hole concentration ? for the high temperature superconductors YBa2Cu3Ox and (La1-xMx)2CuO4. Our results for ? ln Tc/? ln V as a function of Tc describe quite satisfactorily the general trend of the experimental data. Furthermore we show that in the bisoliton model the energy gap ? (in units of Jg3/3, where J is the nearest-neighbour exchange integral and g is the nonlinearity parameter) is an universal function of ?/g. An analogous property is valid for Tc. By fitting the maximum value of Tc we are able also to reproduce the experimental data for Tc(?).