Magneto-Raman signature of chiral phonon in monolayer MoS2*

Helicity-resolved Raman spectroscopy (HRRS) is a useful technique for discerning phonon symmetry in 2D materials. In our HRRS studies of monolayer MoS₂,  we observed a doubly degenerate chiral phonon at around 270 cm^-1. Our wavelength- and temperature-dependent measurements show that this chiral phonon is activated by the A exciton transition in MoS₂. Magneto-Raman spectroscopy measurements revealed phonon Zeeman splitting and a large magnetic moment of this chiral phonon mode. Theoretical calculation is developed to explain the chiral phonon behavior. Our work not only expands the understanding of monolayer MoS₂, but also provides a framework for extending these findings to other two-dimensional hexagonal lattices.