Tailoring Excitonic Excitations in a Strained Quasi-1D Moiré Superlattice

Strains in two-dimensional moiré materials can reshape moiré landscapes and unlock novel excitations and quantum phases. However, optically probing excitonic excitations arising from local strain remains difficult due to the diffraction-limited spot size (typically a few micrometers). In this talk, I’ll present our experimental efforts in probing intralayer exciton resonances down to nanometer-scale, utilizing scanning transmission electron microscopy (STEM) and electron energy-loss spectroscopy (EELS). In a nearly aligned WSe₂/MoSe₂ bilayer, we spatially map the strain-dependent excitonic response. Surprisingly, new excitonic features emerge in the strained quasi-1D moiré superlattice. We will discuss the nature of these excitonic responses, combining four-dimensional scanning transmission electron microscopy (4D-STEM). Our study establishes STEM-EELS as a powerful tool for resolving excitonic excitation at local strains beyond the optical diffraction limit.