Critical behaviors of photoinduced giant permittivity in potassium tantalate

We have demonstrated that a static permittivity of potassium tantalate is dramatically enhanced by band-to-band excitation at low temperatures. A critical behavior has been observed in the relaxation time and the oscillator strength of its Debye-type dispersion. Two models, considering photoinduced mesoscopic clusters formed around excited carriers, can successfully reproduce temperature and carrier-density dependence of the photoinduced effect observed in the experiment.