Quantum materials, materials with properties that are governed by the laws of quantum mechanics describing many-body interactions, have proved promising for the development of various advanced technologies. Many of these materials undergo so-called phase transitions, switching between different physical states that alter how electrons flow through them.

Some previous studies have demonstrated the transition from insulating states to metallic states in quantum materials, via a process called photoexcitation (i.e., the excitation of electrons using light). Yet the opposite transition, from metallic to insulating states, has so far proved difficult to realize using light alone.

Researchers at Columbia University, in collaboration with UC Riverside, recently demonstrated an ultrafast photo-induced metal-to-insulator transition in two-dimensional (2D) moiré heterostructures, quantum materials consisting of 2D layers stacked on top of each other, with a slight misalignment between them.