Giant effective magnetic moments of chiral phonons from orbit-lattice coupling

Circularly polarized lattice vibrations, also known as chiral phonons, carry angular momentum that leads to magnetic response. Recent experiments revealed responses far exceeding prior theoretical predictions within a classical framework. Here, the authors introduce a microscopic model which explains the large magnetic moments of chiral phonons in magnetic materials, resulting from orbit-lattice couplings that hybridize optical phonons with orbital electronic transitions.