Brillouin scattering in polyphenyls. II. Through the incommensurate phases of biphenyl

摘要

Brillouin scattering experiments from room temperature down to liquid helium temperature are reported. Two phase transitions occur in this temperature range atTI=40 K andTII=17 K, but elastic anomalies only happen atTI. Several attempts for the direct phason detection have been found unsuccessful. The elastic anomalies are qualitatively interpreted inside the frame of the Landau theory with simple group theory arguments.