Non-Gaussian conductance noise in disordered electronic systems due to a nonlinear mechanism

Abstract

We present the results of conductance-noise experiments on disordered films of crystalline indium oxide with lateral dimensions $2\phantom{\rule{0.3em}{0ex}}\ensuremath{\mu}\mathrm{m}--1\phantom{\rule{0.3em}{0ex}}\mathrm{mm}$. The power spectrum of the noise has the usual $1∕f$ form, and its magnitude increases with the inverse sample volume down to the sample size of $2\phantom{\rule{0.3em}{0ex}}\ensuremath{\mu}\mathrm{m}$, a behavior consistent with uncorrelated fluctuators. A colored second spectrum is only occasionally encountered (in samples smaller than $40\phantom{\rule{0.3em}{0ex}}\ensuremath{\mu}\mathrm{m}$), and the lack of systematic dependence of non-Gaussianity on sample parameters persisted down to the smallest samples studied $(2\phantom{\rule{0.3em}{0ex}}\ensuremath{\mu}\mathrm{m})$. Moreover, it turns out that the degree of non-Gaussianity exhibits a nontrivial dependence on the bias $V$ used in the measurements; it initially increases with $V$ then, when the bias is deeper into the nonlinear transport regime it decreases with $V$. We describe a model that reproduces the main observed features and argue that such a behavior arises from a nonlinear effect inherent to electronic transport in a hopping system and should be observed whether or not the system is glassy.