Stable and Unstable Thermo – Current States of High Temperature
Superconductors During Current Charging

Vladimir R. Romanovskii, Nikolay A. Lavrov, Vera K. Ozhogina
Russian Research Center ‘Kurchatov Institute’, Moscow 123182, Russia
E-mail: vromanovskii@netscape.net

Abstract – We discuss formation peculiarities of the stable and unstable states in high-Tc superconductors. To understand the basic physical trends, which are characteristic for the current penetration mechanism in high-temperature superconductors, we investigate theoretically the operating states of Bi2212 slab without stabilizing matrix placed in DC external magnetic fields at low coolant temperature. We prove that the temperature of a high-T_c superconductor is not equal to the coolant temperature before instability onset. Therefore, the voltage-current characteristic of a high-T_c superconductor has only a positive slope during continuous current charging. As a result, it does not allow one to find the boundary between stable and unstable thermo – current states. This has to be taken into account during experiments where the critical current of high-T_c superconductors is defined.

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Manuscript received Nov. 23, 2007; accepted January 3, 2008. Reference No. ST17, Category 5.
Based on paper submitted to Proceedings of EUCAS 2007; published in JPCS 98 (2008), paper # 012017