Infrared Hall effect in high-Tc superconductors:: Evidence for non-Fermi-liquid Hall scattering

Infrared (20-120 and 900-1100 cm(-1)) Faraday rotation and circular dichroism are measured in high-T-c superconductors using sensitive polarization modulation techniques. Optimally doped YBa2Cu3O7 thin films are studied at temperatures in the range (15 < T < 300 K) and magnetic fields up to 8 T, At 1000 cm(-1) the Hall conductivity sigma(xy) varies strongly with temperature in contrast to the longitudinal conductivity sigma(xx) which is nearly independent of temperature. The Hall scattering rate gamma(H) has a T-2 temperature dependence but, unlike a Fermi liquid, depends only weakly on frequency. The experiment: puts severe constraints on theories of transport in the normal state of high-T-c superconductors.