Lorentz-force independence of resistance tails for high-temperature superconductors in magnetic fields nearTc

An unusual loss mechanism has been commonly observed in the high-temperature superconductors in a magnetic field near the zero-field transition temperature ${\mathrm{T}}_{\mathrm{c}}$. The resistive transitions associated with this loss in highly c-axis-oriented ${\mathrm{Tl}}_2$ ${\mathrm{Ba}}_2$ ${\mathrm{CaCu}}_2$ ${\mathrm{O}}_{\mathrm{x}}$ thin films are presented as a function of field perpendicular to the c axis, for the current both perpendicular and parallel to the field. The data for these orientations are essentially the same over a span of 5 orders of magnitude below the normal-state resistance. Since the macroscopic Lorentz force is zero for the current parallel to the magnetic field, it can play, at most, a significantly reduced role in this loss mechanism, and our results seriously question any explanation of these losses based on magnetic flux motion.