Configurable Phonon Polarization Responses in Twisted α‑MoO3

Twisting between layered materials in close proximity causes reconstruction of the electron and crystal structures. The resulting reconstruction has received increasing attention due to the realization of magic-angle superconductivity, moiré excitons, and moiré ferroelectricity. However, demonstrations of such concepts for phonon polarization have been very limited. Here, we reported on the systematic angle-dependent polarized Raman (ADPR) investigations on the twisted bilayer (tBL) α-MoO3 with each layer in a thickness of ∼14 nm. Under 532 and 633 nm excitation, (i) the Raman intensity (I) of representative Mo–Oc symmetric stretching vibration phonon mode (SVPM) at 818 cm–1 and rigid MoO4 translational vibration phonon mode (TVPM) at 156 cm–1 decreases monotonically with the twist angle (φ) increase and (ii) the polar plots of both modes were tuned from axial symmetry to central symmetry by φ increase. The dependence of I and symmetry of both modes on φ were described semiquantitatively by applying the classical Placzek approximation and the interference effect. Our findings unravel the complex interaction between the twisted layer configurations and phonon behaviors of α-MoO3, providing valuable insights into the anomalous phonon polarization responses in low symmetric two-dimensional materials and potentially facilitating the development of technologies based on tunable phonon polarization.