Evidence for photoactivated defect induced dielectric anomalies in CuCL

Dielectric measurements of optically irradiated single crystal and composite samples of CuCl prepared and stored under carefully controlled conditions have revealed anomalies in both the capacitance and tan δ at 220 K. At low temperature the capacitance shows a peak versus increasing integrated photon flux which is interpreted as increasing photoinduced Cu° defect precipitate. The results are reproducible and correlate with earlier reports of anomalous diamagnetism (high temperature superconductivity precursor) in CuCl. The observation of a large low frequency dielectric constant in CuCl supports the existence of a low frequency (soft) phonon mode in the CuCl-Cu precipitate composite which could provide a mechanism for high temperature superconductivity.