Bias Exponent of Resistance Noise as a Probe for Disordered Systems

Abstract

The power spectral density Sv(f) of voltage fluctuations in the Ohmic regime of a system varies with voltage V as Sv(f) ≈ Vβ where β is the bias exponent. The equilibrium resistance fluctuation in a homogeneous system provides β = 2 but in disordered systems, we show that β strongly depends on quenched disorder and temperature and is less than 2 in the Ohmic region. At a fixed temperature, β remains nearly equal to 2 at low disorder and decreases from 2 to 1 with the increase in disorder. Interestingly, similar variation in β is observed with the change in temperature from high to low at a fixed quenched disorder. These two cases favor weak localization in the limit of high disorder or low temperature. Experimental results on manganite compounds indicate that the bias exponent β could be used as a sensible nondestructive parameter to identify the existence of a phase transition evolved during the course of investigation. Remarkable correlations between the electrical transport and the power spectral density Sv(f) are observed and explained with the help of inhomogeneous distribution of currents. The results are also supported by the non‐Gaussian nature of the second spectrum of 1/f noise at different temperatures.