Exciton-activated effective phonon magnetic moment in monolayer MoS2

Chiral phonons are lattice vibration modes in which the atomic circular motions produce nonzero angular momentum. In monolayer MoS₂, the authors demonstrate here a chiral phonon mode at ~270 cm^-1 that is activated by resonant excitation of the bright exciton. Under an out-of-plane magnetic field, this mode exhibits large Zeeman splitting, which corresponds to an effective magnetic moment of ~2.5 {μ}B. This study will stimulate research on the effective magnetic moments that emerge from the interplay between chiral phonons and the valley degree of freedom.