Electrically driven inhomogeneous phase transition in CuIr₂S₄

Comparable energy scales of dominant interactions determining electronic phases and relatively smaller energy barrier separating different phases makes 5d electronic systems sensitive to an external perturbation (e.g. temperature, electric field, strain). CuIr₂S₄, a 5d transition metal compound with spinel structure, shows a hysteretic metal-insulator transition at T_c ~ 231 K (on cooling) accompanied with crystal symmetry lowering from high-temperature cubic (metallic) to low-temperature tetragonal (insulating) phase. The system also exhibits electric field-driven hysteretic switching from insulating to metallic phase below T_c. Transport and resistance noise spectroscopy were carried out: at temperatures well below T_c, the transition is characterized by a single abrupt switching and the power spectral density (PSD) of the noise varies smoothly across the transition. Approaching T_c, on the other hand, switching happens with multiple, step-like jumps and the PSD is found to increase significantly. The melting of long-range charge ordering near T_c likely increases the local inhomogeneity thereby resulting in increased PSD. Results will be discussed in the context of microscopic conduction mechanisms across thermal and electrical driven transitions in strongly correlated systems.