Chiral phonon mode with non-zero angular momentum

The interaction between spin, lattice, and charge in correlated materials gives rise to interesting properties. A recent observation of chiral phonons in magnetic material provides a new perspective for phonon excitation. We will discuss the origin and the effects of chiral phonons on spin relaxation and the optical properties of molecular magnets. The best-performing nanomagnets usually exhibit very high symmetry, i.e., C₅/D_5h, their phonon spectra in terms of reducible vector representation can be described by direct sum of nA^'s and nE^'s. The presence of symmetry character nE^'s indicates that there will be two degenerate phonon modes ω_± with angular momentum, L_z = ±1. The effect of chiral phonons can be observed in magneto-IR (Raman) spectroscopy by breaking time-reversal symmetry using a magnetic field. The observation of chiral phonon has various applications in quantum technology, such as coherent transport of spin information.