Thermally activated dissipation in Bi/sub 2. 2/Sr/sub 2/Ca/sub 0. 8/Cu/sub 2/O/sub 8+//sub delta/

Abstract

A new dissipation behavior is reported in superconducting Bi/sub 2.2/Sr/sub 2/Ca/sub 0.8/Cu/sub 2/O/sub 8+//sub delta/ for all temperatures below T/sub c/ and all magnetic fields exceeding H/sub c//sub 1/. 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 energy U/sub 0/(H,phi). 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/sub c//sub 1/ determined by the activation energy as the only parameter.