Polarized Moire Phonon and Strain-Coupled Phonon Renormalization in Twisted Bilayer MoS2

The ability to control the atomic-scale behavior in quasi-two-dimensional crystals via twisting the vicinal layers and generating patterned moire potentials provides an additional degree of freedom to study correlated physics. Under the existence of macroscopic external parameters such as strain, we study the high-frequency Raman active vibrational modes of chemical vapor deposition (CVD)-grown monolayer, stacked (AA ' and AB), and twisted bilayer MoS2. The polarized Raman scattering, being an efficient characterization tool for these moire ' structures, is employed to investigate the effects of strain on the different phonon modes. The recently discovered moire phonons (FA(1g)), i.e., zone center phonons in a twisted bilayer MoS2, stem from the folding of the off-center phonons of its monolayer constituents and are found to be Raman polarized. Moreover, the Raman shift impressions of these moire ' phonons in twist angle in the range between 0 and 30 degrees are reproduced, showing the strain-coupled modifications of the previously reported sinusoidal behavior. Our findings establish an effective method to probe the strain-induced anisotropy in twisted van der Waals systems using polarized Raman spectroscopy showing future directions to moire-related physics.

Automated summary

Controlling the atomic-scale behavior in quasi-two-dimensional crystals through twisting the vicinal layers and generating patterned moire potentials provides additional freedom for studying correlated physics. In this study, we investigate the effects of strain on different phonon modes in monolayer, stacked, and twisted bilayer MoS2 using polarized Raman scattering. Our findings show the strain-coupled modifications of moire phonons and establish a method to probe the strain-induced anisotropy in twisted van der Waals systems using polarized Raman spectroscopy.