Pressure Tuning of Minibands in MoS2/WSe2 Heterostructures Revealed by Moiré Phonons

Hydrostatic pressure is an underexplored tuning knob to study moire systems. Here a MoS2/WSe2 heterostructure is compressed and the enhancement in the moire potential strength is quantified via moire-activated Raman modes. Moire superlattices of two-dimensional heterostructures arose as a new platform to investigate emergent behaviour in quantum solids with unprecedented tunability. To glean insights into the physics of these systems, it is paramount to discover new probes of the moire potential and moire 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 moire potential. Here we use high pressure to tune the minibands in a rotationally aligned MoS2/WSe2 moire heterostructure, and show that their evolution can be probed via moire phonons. The latter are Raman-inactive phonons from the individual layers that are activated by the moire potential. Moire 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 moire potential strength. By comparing the experimental and calculated pressure-induced enhancement, we obtain numerical estimates for the moire potential amplitude and its pressure dependence. The present work establishes moire phonons as a sensitive probe of the moire potential as well as the electronic structures of moire systems.