Scientists at EPFL and the University of Geneva have combined two powerful, cutting-edge techniques to uncover the physics behind an exotic phase transition that turns a metal into an insulator. The materials they looked at are rare-earth nickelates, which are of great interest for innovating new approaches in electronics.
“Phase transitions” are a central phenomenon in physical sciences. Despite being technical-sounding, they are actually something we all experience in everyday life: ice melting into liquid water, or hot water evaporating as steam. Solid, liquid, and gas are three well known “phases” and, when one turns into another, that is a phase transition.
Rare-earth nickelate oxides, also called nickelates, have attracted a lot of interest from researchers because they display an electronic phase transition, which may be exploited in future electronic devices. This particular phase transition consists of turning from a metallic state that conducts electricity into an electrically-insulating state as temperature drops.
Behind this behaviour is a strong interaction between the electronic properties of these compounds and their “lattice” structure – the well-ordered arrangement of atoms that forms a crystal. However, uncovering the true nature of this metal to insulator phase transition in nickelates, and being able to control it for potential electronic devices, requires knowing how each characteristic phase emerges and evolves across the transition.
Source: “Nano-mapping phase transitions in electronic materials”, Nik Papageorgiou, EPFL News