Anomalous photoinduced current transients in the nematic phase are experimentally observed by illuminating a liquid-crystal sample with a xenon-flash-lamp pulse while applying a dc voltage. The response time is fast, of the order of a microsecond, and independent of the magnitude of the applied voltage. The peak current is independent of the wavelength of the light and displays a critical response near the nematic-isotropic phase-transition temperature. Pyroelectricity in nematic liquid crystals is proposed as the physical origin of the phenomenon.

• Received 17 January 1989

DOI:https://doi.org/10.1103/PhysRevLett.63.555