Dielectric spectroscopy and nonequilibrium phase transitions in TlGaSe_2 layered crystals

摘要

The real and imaginary parts of the dielectric function of TlGaSe_2 single crystals are investigated in the frequency range 30 Hz-13 MHz and at temperatures 80 K-300 K. A low frequency dispersion due to the interfacial polarization within the crystals is observed. The temperature dependence of relaxation time is obtained in a wide temperature region. A well distinguished anomalous rise of relaxation time has been established in the 145 K-190 K temperature range for the first time far from the traditional phase transitions known in TlGaSe2 crystals. It is shown that the observed behaviour of relaxation time is due to instabilities in the electronic subsystem revealing themselves as a non-equilibrium phase transition. A close relationship between the observed anomaly and anomalous behaviour of the various physical parameters of the investigated crystals is proposed.