Noise spectroscopy study of metal-insulator transition in CuIr₂S₄

Single crystals of the CuIr₂S₄ exhibit a metal-insulator transition (MIT) at a critical temperature (T_c ) ∼ 231 K, accompanied by simultaneous charge ordering and spin dimerization, making it an interesting system to study the interplay of interaction among many degrees of freedom. By employing low-frequency electrical noise spectroscopy, we observe that the power spectral density (PSD) of the resistance fluctuations peaks around T_c likely due to the formation of domains of opposite phase. The ultra-low frequency window of our measurements serves as a tool to measure the increased scattering of charge carriers near T_c, due to nucleation, pinning and/or propagation of domains. The probability density function (PDF) of the fluctuations in the transition region shows a significant deviation from the expected Gaussian behavior further supporting the intermixing of phases near T_c. In addition, an abrupt phase transition with a threshold behavior can also be triggered electrically from the insulating phase. The analysis of the PSD, PDF and 1/f behavior suggests a significant role of the domains in the electrically driven case too.