Electronic states at polar/nonpolar interfaces grown on SrTiO3 studied by optical second harmonic generation

A voltage-noise analysis of FeTe0.5Se0.5 thin films has revealed the existence of nonlinear fluctuations above an electric field bias threshold. Below this threshold the fluctuations are standard and compatible with the presence of electron- and hole-type carriers, and it has been possible to evaluate the value of the Hooge noise parameter. Above the electric field bias threshold and at temperatures higher than 70 K, an increased nonlinear 1/f noise is found with a power exponent scaling with the temperature squared. Several possible theoretical interpretations are considered and discussed. © 2013 IOP Publishing Ltd.