SPICE Workshop on Chiral Phonons, July 29th - 31st 2025
Jong Seok Lee
In crystalline solids, chiral phonons are capable of carrying angular momentum, which can be transferred to other quasiparticles through their interactions with electrons, spins, and orbital moments. In this study, we present a straightforward yet effective method for observing the dynamics of thermalized chiral phonons in an artificial superlattice formed by ferromagnetic metallic SrRuO3 and non-magnetic insulating SrTiO3. Following the photo-induced ultrafast demagnetization in the SrRuO3 layer, we detected an additional magneto-optic signal in the superlattice that is not present in SrRuO3 single films. This emerging magneto-optic signal displays thermally-driven dynamic characteristics and shows a distinct correlation with the thickness of the non-magnetic SrTiO3 layer, suggesting that it arises from thermalized chiral phonons. Through numerical calculations accounting for magneto-elastic coupling, we found the time evolution of lattice angular momentum to be in excellent agreement with our experimental observations. If time allows, we discuss more about distinct roles of acoustic chiral phonons on the thermal transport.