Infrared Hall effect in underdoped and optimally doped LSCO

We report a study of magneto-optical properties in the mid-infrared region of a series of La${}_{2-x}$Sr${}_x$CuO${}_4$ samples with hole doping level ranging from severely underdoped ($x=0.03$)to optimally doped ($x=0.15$). The Faraday rotation and circular dichroism are measured in a magnetic field of 8 Tesla and in a temperature range between 30K and 300K. The doping and temperature dependence of infrared Hall angle is found to be understood within a simple Drude model. A significant increase of Hall frequency is observed when the hole doping level is reduced from optimal doping, which is compared with models of the pseudogap.