Revealing quantum geometry effects in magic angle twisted bilayer graphene using the circular photogalvanic effect
Researchers used a circular photogalvanic effect (CPGE) study on magic angle twisted bilayer graphene illuminated by near-infrared light to probe quantum geometry and symmetry. They found that the system's point group symmetry is lowered to C1, suggesting a Berry curvature dipole exists. This effect is driven by interband interference and pumped BCD mechanisms, revealing complex electronic states near specific electron fillings.