Thermal peculiarities of the electric mode formation of high temperature superconductors with the temperature-decreasing n-value

Formation peculiarities of the static thermo-electric modes that may be observed in high temperature superconductors at the DC current are studied taking into consideration the temperature-decreasing dependence of the power exponent (n-value) of the voltage-current characteristic of a superconductor. The used models are based on the steady zero-dimensional models. The study is made for the conduction-cooling and liquid coolant conditions at different operating temperatures. It allows us to investigate the non-isothermal voltage-current characteristic of Bi2223 and YBCO that rooted the development of their stable and unstable thermo-electric regimes. It is shown that the temperature dependence of an n-value may lead, first, to usually observed static voltage-current and temperature-current characteristics having one stable and unstable parts and, second, to unexpected thermo-electric states in the temperature range that is closed to its transition into the normal state. It is a result of the formal temperature variation of the differential resistivity of a superconductor depending on its temperature-decreasing critical current density and n-value. As a result, to describe correctly thermal stability conditions and analyze theoretically the quench processes in high temperature superconductors, the temperature dependences of their critical current density and n-value must be restored before the transition of a superconductor into the normal state as carefully as possible.