Infrared optical response of LuFe2O4 under dc electric field

We applied dc voltage (V) to the LuFe2O4 single crystal and measured the V-dependent optical reflectivity. As V increases, an optical absorption band appears at the mid-infrared frequency range which we could identify as resulting from the dc electric (E) field. We discuss possible connection of this novel electro-optical effect with the strongly correlated states in LuFe2O4. In the mean time, a reflectivity level change is seen in the IR similar to visible frequency range by the V application due to the Joule heating of the sample.