High-field breakdown of the superconducting critical state in Bi₂Sr₂CaCu₂O single crystals

The critical state in Bi₂Sr₂CaCu₂O single crystals is found to become unstable at low temperatures and high-magnetic fields. Reproducible and almost periodic flux jumps developed at high fields only are qualitatively different from those known in conventional superconductors and predicted by existing models. The breakdown can occur in the regime considered to be stable, which compromises the existing criteria for the potential high-field applications of high-T_c materials.