Search for: All records

Since the discovery of two-dimensional transition metal dichalcogenide monolayers as direct bandgap semiconductors with pronounced room-temperature exciton transitions, research on excitons and polaritons in these materials has exploded worldwide. Here, we give an introductory tutorial on the basic properties of excitons and polaritons in these materials, emphasizing how they are different from those in conventional semiconductors, and discuss some of the most exciting new phenomena reported. 

Abstract Twisted transition metal dichalcogenide (TMD) bilayers have enabled the discovery of superconductivity, ferromagnetism, correlated insulators, and a series of new topological phases of matter. However, the connection between these electronic phases of matter and the underlying band structure singularities has remained largely unexplored. Here, combining magnetic circular dichroism and exciton sensing measurements, we investigate the influence of a van Hove singularity (vHS) on the correlated phases in bilayer WSe₂with twist angle between 2 and 3 degrees. By tuning the vHS across the Fermi level using electric and magnetic fields, we observe Stoner ferromagnetism below moiré lattice filling one and Chern insulators at filling one. The experimental observations are supported by the continuum model band structure calculations. Our results highlight the prospect of engineering electronic phases of matter in moiré materials by tunable van Hove singularities.