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 dichroi sm are measured in high-T-c superconductors using sensitive polarization mo dulation techniques. Optimally doped YBa2Cu3O7 thin films are studied at te mperatures 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 temperatur e in contrast to the longitudinal conductivity sigma(xx) which is nearly in dependent of temperature. The Hall scattering rate gamma(H) has a T-2 tempe rature dependence but, unlike a Fermi liquid, depends only weakly on freque ncy. The experiment: puts severe constraints on theories of transport in th e normal state of high-T-c superconductors.