The mixed-state Hall effect of twinned YB${\mathrm{a}}_2$C${\mathrm{u}}_3$${\mathrm{O}}_7$ crystals after heavy-ion irradiation clearly showed that the strong pinning induced by columnar defects not only modifies the scaling behavior between the Hall resistivity and longitudinal resistivity, but affects the temperature dependence of the Hall conductivity. For the irradiated crystals, the scaling exponent at 4 T was found to be $1.5\pm 0.1$ compared to $2.0\pm 0.2$ for the unirradiated one. The temperature dependence of the Hall conductivity of the irradiated crystals exhibited a clear deviation from that of the unirradiated one at low temperatures.

• Received 10 July 1995

DOI:https://doi.org/10.1103/PhysRevLett.76.2993