Electric-field switching of g-wave phonon chirality in ferroelectric BaTiO3

Key Points:

• Researchers have demonstrated non-volatile, reversible switching of phonon angular momentum (PAM) in ferroelectric BaTiO3 (BTO) thin films by controlling polarization with an electric field, using circularly polarized resonant inelastic X-ray scattering (RIXS) to probe chiral phonons.
• Chiral phonons, which carry angular momentum through atomic vibrations breaking improper rotational symmetry, are shown to have their handedness inverted upon switching the ferroelectric polarization, confirming the coupling between lattice chirality and electric order.
• The study establishes that PAM in BTO arises from broken inversion symmetry associated with Ti4+ displacement, and that the circular dichroism (CD) observed in RIXS directly measures the orbital angular momentum of oxygen atoms in phonon modes.
• Experimental results align with density functional theory (DFT) calculations predicting phonon modes with finite chirality, and the observed switching behavior follows the crystallographic symmetry, demonstrating gyroelectric control of chiral phonons.
• This work opens pathways for tuning angular momentum as a degree of freedom in phononics, with potential applications in low-power electronics, ultrafast magnetic switching, and neuromorphic computing through controlled lattice dynamics and phonon–magnon coupling.