Dissipation Below T sub c in the High Temperature Superconductors

A new dissipation behavior below T sub c is reported of single crystal Bi sub 2 Sr sub 2 CaCu sub 2 O sub 8 and Ba sub 2 YCu sub 3 O sub 7. The electrical resistivity below T sub c is thermally activated and can be described by an Arrhenius law over several orders of magnitude. For Bi sub 2 Sr sub 2 CaCu sub 2 O sub 8 we find a simple description: rho(T,H,phi)=rho sub o exp(-U sub o (T,H)/k sub B T). 

Here, rho sub o is magnetic field and orientation independent and has a value about three orders of magnitude larger than the room temperature resistivity. The activation energy U sub o depends weakly on magnetic field and orientation, and has values between 300K and 3000K. For Ba sub 2 YCu sub 3 O sub 7 the activation energies are larger by one to two orders of magnitude.