Spin–orbit exciton–induced phonon chirality in a quantum magnet

• Phonons are important collective excitations in materials. Typically, they do not respond to magnetic field and do not carry a magnetic moment (chirality).
• Phonon chirality can be induced via two mechanisms (i) adiabatic evolution with electronic states that break time-reversal symmetry (e.g. magnetism) and (ii) phonon induced mixing of different electronic energy levels.
• A quantum magnet CoTiO3 hosts interesting bosonic excitations such as topological magnons and spin–orbit excitons
• The interaction between spin–orbit excitons and phonons endows chirality to two  phonon modes and leads to large phonon magnetic moments observed in magneto-Raman spectra

UT-Austin MRSEC
DMR-1720595