Thermally activated two-level systems in superionic conductors
Abstract In superionic crystals, as well as in vitreous superionic conductors, the monotonous growth (almost linear) of the specific heat C ( T ) and the thermal conductivity λ ( T ) in a wide temperature range of superionic phase has been obtained. Such behaviour takes place in a temperature region that considerably exceeds the Debye temperatures of the investigated materials. It is shown that in the high temperature region the growth of C , and respectively λ , may reflect a relaxation interaction of high frequency phonons with two-level systems (TLS). The examination of excess heat capacity Δ C ( T ) in the framework of the TLS model allows to find a concentration of migration ions, which is in good accordance with an experimental data.