Selective soft mode heating in a ferroelectric film

The effect of electromagnetic radiation with a frequency of f ∼ 0.3 THz on the temperature of a soft-mode phonon subsystem in a (Ba,Sr)TiO3 film has been studied. Features of the temperature regimes in a ferroelectric capacitor structure were revealed using a capacitive thermometer and a thermocouple. It is established that, at a pumping radiation intensity of ∼6 mW/mm2, the overheating of soft-mode phonons, as evaluated from a change in the capacitance of a planar capacitor, exceeds the integral overheating of this capacitor measured using a thermocouple. Conditions determining the nonequilibrium state of the soft-mode phonon subsystem in a ferroelectric film are analyzed.