Switching of chiral phonons in ferroelectrics

Chirality is one of the major topics in recent condensed matter physics due to chirality-induced functionalities and topological textures relating to symmetry breaking, e.g., in van der Waals materials. Driving a chiral mode can be a unique approach to manipulating ultrafast emergent phenomena and corresponding dynamics. Recently, our group successfully observed chiral phonons in chiral crystals of α-quartz using circularly polarized RIXS [Nature 618, 946 (2023)]. In principle, chiral phonons exist in other non-centrosymmetric crystals, such as polar (ferroelectric) materials, which we recently observed for a non-chiral but polar crystal LiNbO3. This result suggests that we can manipulate phonon chirality by flipping the polarization. We plan to demonstrate in situ electric field switching on free-standing (FS) films of BaTiO3 (BTO) using circularly polarized RIXS at the oxygen K-edge. Our results will open the possibility of manipulating phonon chirality and associated phonon angular