Nanoscale Lattice Dynamics in Hexagonal Boron Nitride Moiré Superlattices*

Moiré superlattices enable a new means to tune the properties of quantum materials. Past research has found extensive control of electronic properties with moiré effects. There, scanning probe measurements have supported those measurements with microscopic origins for the observations. However, less is known about moiré vibrational properties, with measurements limited to far-field Raman spectroscopy. Here, we present a deterministic procedure for obtaining large-area moiré hexagonal boron nitride (hBN) domains. We use near-field infrared imaging to study the strong in-plane hBN phonon resonance in a moiré superlattice with 250-nm periodicity. We explain the observations with mechanical relaxation simulations and vibrational ab-initio calculations. By revealing a strong interplay between vibrational, mechanical, and atomic registry so far unidentified in far-field experiments, we take a larger step towards moiré tunability of quantum material vibrational properties.