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Phonon-Driven Multipolar Dynamics in a Spin-Orbit Coupled Mott Insulator

Shaking electrons or atoms with light can induce remarkable nonequilibrium many body states in solid-state crystals as well as ultracold atoms. In recent years, rapid advances in ultrafast and THz optics have led to the ability to resonantly excite specific orbital transitions and phonon modes in solids , providing a distinct pathway to control broken symmetry states including ferroelectricity , superconductivity , and magnetism.
Crystal structure for the double perovskite system

Publication Date: June 18, 2025

Authors: Kathleen Hart, Ruairidh Sutcliffe, Gil Refael and Arun Paramekanti

Abstract:

Motivated by advances in pump-probe experiments and light-driven phenomena, we theoretically study the impact of pumped and driven phonons in Mott insulators which host multipole moments, thus going beyond conventional dipolar magnetism. As a case study, we examine pseudospin- Mott insulators hosting quadrupolar and octupolar moments, and investigate the effect of resonantly exciting phonon modes which couple linearly to the quadrupoles. We show that this leads to multipolar precession, with the backaction resulting in pseudochiral phonon dynamics in the octupolar ordered phase. We further study the impact of a short-time two-phonon drive, showing that it can induce the buildup of octupolar order or even switch its sign on picosecond timescales. Our results are obtained using a Monte Carlo code incorporating phonons, molecular dynamics simulations to numerically integrate the coupled spin-phonon equations of motion, and analytical Floquet theory. Our work shows how driven phonons can probe and control hidden orders in solids.

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