Pressure-tuning of minibands in MoS₂/WSe₂ heterostructures revealed by moiré phonons

Moiré superlattices of two-dimensional heterostructures arose as a new platform to investigate emergent behavior in quantum solids with unprecedented tunability. To glean insights into the physics of these systems, it is paramount to discover new probes of the moiré potential and the moiré minibands, as well as their dependence on external tuning parameters. Hydrostatic pressure is a powerful control parameter, since it allows to continuously and reversibly enhance the moiré potential. In this talk, I will discuss our recent work [1] where we used high pressure to tune the minibands in a rotationally-aligned MoS₂/WSe₂ moiré heterostructure, and showed that their evolution can be probed via moiré phonons. The latter are Raman-inactive phonons from the individual layers that are activated by the moiré potential. Moiré phonons manifest themselves as satellite Raman peaks arising exclusively from the heterostructure region, increasing in intensity and frequency under applied pressure. Further theoretical analysis reveals that their scattering rate is directly connected to the moiré potential strength. By comparing the experimental and calculated pressure-induced enhancement, we obtain numerical estimates for the moiré potential amplitude and its pressure dependence. Our results indicate a considerable flattening of the minibands upon compression up to 5 GPa due to the increase of the moiré potential strengh. The present work establishes moiré phonons as a sensitive probe of the moiré potential and of the electronic structures of moiré systems.

[1] Pimenta Martins, L.G.*, Ruiz-Tijerina*, D. A., et al . "Pressure tuning of minibands in MoS₂/WSe₂ heterostructures revealed by moiré phonons." Nature Nanotechnology (2023): 1-7. DOI: https://doi.org/10.1038/s41565-023-01413-3. * Equal contirbution