Researchers at UC Santa Barbara have identified a new state of matter known as a “bosonic correlated insulator,” formed from excitons, which are bound pairs of electrons and holes. This discovery was made by stacking two similar lattices of tungsten diselenide and tungsten disulfide in a twisted arrangement, creating a moiré pattern that facilitated interactions between excitons. Traditionally, the study of quantum materials has focused on fermions, which do not occupy the same energy level, while bosons, such as excitons, can coexist in this manner due to their whole integer spins. The team utilized a technique called “pump-probe spectroscopy,” involving powerful light sources to induce exciton formation and monitor their behavior. Interestingly, at a certain density, the excitons became immobile, resulting in a highly ordered crystalline state that exhibited insulating properties. This breakthrough challenges previous conceptions of bosonic behaviors, establishing a platform to explore many-body phases in real materials and potentially uncover new exotic bosonic materials. The findings offer significant insights into condensed matter physics, suggesting that similar approaches could lead to understanding and development of materials with unique properties. The study is detailed in the journal Science.
