Phonon-driven multipolar dynamics in spin-orbit coupled Mott insulators

Motivated by ongoing work on pump-probe experiments and Floquet driven magnets, we theoretically study the impact of pumped and driven Einstein phonons with weak dissipation in multipolar Mott insulators. For Mott insulators with pseudospin-$1/2$ non-Kramers doublets hosting octupolar and quadrupolar moments, we show that pumping the ${\cal E}_g$ phonon modes which couple linearly to the quadrupoles leads to characteristic chiral phonon dynamics below the octupolar ordering transition. We also explore steady states in the presence of continuously driven phonons, showing that a coherent two-phonon drive with a suitable phase choice can be used to 'train' octupolar order or even switch its sign. For spin-$1$ magnets, which host dipolar and quadrupolar moments, we show that one-phonon and two-phonon drives can generate Floquet flavor-wave excitations and induce dipolar magnetization. Our results are obtained using a generalized $SU(N)$ Monte Carlo for the multipolar degrees of freedom with numerical integration of the coupled spin-phonon equations of motion. Our work opens up pathways to explore phonon-driven dynamics in multipolar magnets.
Comment: 7 pages+SM, revised, added refs