Dissipation in High Temperature Superconductors

A new dissipation behavior is reported in single crystal Bi sub (2.2) Sr sub 2 Ca sub (0.8) Cu sub 2 O sub (8+delta) for all temperatures and all magnetic fields exceeding H sub (c1). The electrical resistivity is thermally activated and can be described by an Arrhenius law over several orders of magnitude in resistivity: rho(T,H,phi)=rho sub o exp(-U sub o(H,phi)/T), with a single prefactor rho sub o and a magnetic field and orientation dependent activation energy U sub o. The prefactor rho sub o is three orders of magnitude larger than the room temperature resistivity, rho sub n=140microohmcm. The activation energy depends weakly on magnetic field and orientation, and is relatively small (300K3000K).