Infrared measurement of a Tl₂Ba₂CaCu₂O_8-x film

A preliminary report of the a-b plane reflectivity of a Tl2Ba2CaCu2O8-x film (Tc ≅ 110K) is presented. The plasma edge occurs at ≅ 2000cm-1, which is quite unexpected because it implies an effective carrier density that is an order of magnitude less than obtained in other high temperature CuO superconductors. © 1989.