Generating in-situ Heterostrain of Moiré Superlattice Heterostructures

Moiré superlattices of van der Waals semiconductors have emerged as a highly tunable material platform to study strong electron correlations and simulate Hubbard model physics in two dimensions. Electrostatic gating enables a high degree of control over electron density and interlayer coupling; however, much of the physics of moiré superlattices is set by the geometric properties of lattice mismatch and relative twist angle, which are selected during device fabrication and cannot generally be altered in situ. In this talk, I will discuss a technique for generating and tuning in situ heterostrain, which enables dramatically altering the moiré wavelength and symmetry by applying different amounts of uniaxial strain to each layer in a transition metal dichalcogenide moiré superlattice. I will describe the experimental apparatus and device fabrication approach we use to achieve heterostrain and show preliminary evidence for the presence of heterostrain obtained with a combination of atomic force microscopy and cryogenic optical measurements. Finally, the possibility of applying heterostrain to a fully dual-gated moiré superlattice and the associated challenges will be covered.