Thermally Activated Dissipation in Bi2.2Sr2Ca0.8Cu2Oa+δ

A new dissipation behavior is reported in superconducting Bi2.2Sr2Ca0.8Cu2Oa+δfor all temperatures belowTc and all magnetic fields exceeding Hc1. The current-independent electrical resistivity is thermally activated and can be described by an Arrhenius law with a single prefactor and a magnetic-field-and orientation-dependent activation energyU 0 (H,ø).This behavior is markedly different from past observations and will be discussed in terms of flux creep and flux flow. This thermally activated behavior implies a finite resistance at all temperatures and all fields exceeding H c1 determined by the activation energy as the only parameter.