The anisotropic conductivity of a series of tilted Nd_{ 1.85}Ce_{ 0.15}CuO_{ 4-\delta} thin films was measured by quasioptical spectroscopy in the frequency range 3cm^{ -1}<\nu <40cm^{ -1}. Two characteristic features have been observed in the low-temperature transmission spectra. The first one at \nu = 12cm^{ -1} was shown to reflect the c-axis plasma frequency of Nd_{ 1.85}Ce_{ 0.15}CuO_{ 4-\delta}. The second feature represents a new mixed ab-plane/c-axis excitation. The frequency of this resonance may be changed in a controllable way by rotating the polarization of the incident radiation.
Categories: cond-mat.supr-con