Circular Dichroic RIXS Study of Chiral Phonon Current in BIBO Crystal

Condensed matter physics has recently witnessed a resurgence of interest in the subject of chirality. This is dueto the possibility of chirality-induced functionalities and topological textures, e.g., in topological van der Waalsmaterials. In addition, the driving of a chiral mode offers a unique approach to manipulating phenomena whichbreak time reversal symmetry on ultrafast timescales. Recently, our group successfully observed chiral phononsin α-quartz, a prototypical chiral crystal, using circular dichroism in resonant inelastic x-ray scattering, CD-RIXS. However, manipulating chirality remains a challenge. To address this, we plan to apply a heat gradientto a chiral crystal which will change the total phonon angular momentum by re-populating the chiral acoustic modes. This creates a chiral phonon current with the chirality defined by the gradient. We plan to observethe non-equilibrium change in left-/right-handed chiral phonon populations using CD-RIXS at the O K-edge.