Rugged landscape at spinodal criticality*

We conducted experimental investigations to explore the nature of slow thermodynamic fluctuations through low-frequency resistance noise spectroscopy in thin films of NdNiO3 in its metastable phase. NdNiO3 is a well-studied example of an electron correlation-driven insulator-to-metal phase transition, accompanied by a structural transition that also undergoes abrupt hysteresis phase transitions. Our experiments have revealed that this transition is primarily governed by spinodal-like criticality, which includes characteristics such as critical slowing down and critical opalescence. Furthermore, in the vicinity of the spinodals, the resistance fluctuations exhibit distinctive signatures of metastability, including a separation of time scales. This qualitative distinction in the nature of fluctuations suggests the emergence of ruggedness within the spinodal landscape.