Peculiarities of dependence on temperature of electrical resistance of high-Tc superconducting composites

The effect of the nonlinearity type of voltage-current characteristic on electrical resistivity of a high-T_c superconducting composite and its influence on the current sharing mechanism is discussed. The obtained results are compared with the simulations made in the framework of the existing thermal stabilization theory based on the model assuming a jump transition from a superconducting state to a normal one. It is shown that the jump-like model incorrectly describes the electrical resistivity of the high-T_c superconducting composite in a wide range of temperature change. As a consequence, a priori defined critical current of a high-T_c superconducting composite and the temperature of the resistive transition, after exceeding which the transport current begins to share between the superconducting core and the matrix according to the existing thermal stabilization theory, have no physical meaning. Accordingly, the real temperature dependence of the electrical resistivity of a high-T_c superconducting composite, which, first of all, is a nonlinear function of a continuously increasing voltage-current characteristic, must consider. As a result, the boundaries of the existing theory will be extended since the stable operating currents may be higher than a priory defined critical current of high-T_c superconducting composites. (paper)