Giant moire trapping of excitons in twisted hBN.

Excitons in van der Waals (vdW) stacking interfaces can be trapped in ordered moire potential arrays giving rise to attractive phenomenons of quantum optics and bosonic many-body effects. Compare to the prevalent transition metal dichalcogenides (TMDs) systems, due to the wide bandgap and low dielectric constant, excitons in twist-stacked hexagonal boron nitride (hBN) are anticipated trapped in deeper moire potential, which enhances the strength of interactions. However, constrained by the common low detectivity of weak light-emitting in the deep-ultraviolet (DUV) bands, the moire excitons in twisthBN remain elusive. Here, we report that a remarkable DUV emitting band (peak located at ~260 nm) only emerges at the twisted stacking area of hBN, which is performed by a high collection efficiency and spatially-resolved cathodoluminescence (CL) at room temperature. Significant peak redshifting contrast to defect-bound excitons of bulk hBN indicates the giant trapping effects of moir\'e potential for excitons. The observation of deeply trapped excitons motivates further studies of bosonic strongly correlation physics based on the twist-hBN system.