Femtosecond response of optical constants due to charge-transfer excitations in Nd2CuO4

Abstract We have performed femtosecond reflectivity ΔR / R and transmissivity ΔT / T measurements in Nd 2 CuO 4 thin film at 80 and 300 K. We have derived time variations of Δϵ ′ and Δϵ ′′ from transient data of ΔR / R and ΔT / T . Assuming a Lorentz oscillator model consisting of three oscillators, we obtain spectra of the real part ϵ ′ and imaginary part ϵ ′′ of dielectric function from the measured reflectivity and absorption spectra in the visible-uv region. The absorption bands in the visible region are assigned to in-plane charge-transfer (CT) excitations, and relaxation times of CT excitations are found to be 0.6 and 1.0 ps.