Dual-circular Raman optical activity of axial multipolar order

Abstract: Multipolar order, such as octupolar order, is one of the key concepts of condensed matter physics, particularly in light of elusive hidden orders. However, its experimental identification remains challenging due to the absence of direct coupling to conventional external stimuli. In this study, we propose that dual-circular Raman scattering serves as a detection of multipolar anisotropies. By combining symmetry analysis with microscopic tight-binding calculations, we demonstrate that both time-reversal-even ($\theta$-even) and time-reversal-odd ($\theta$-odd) axial multipolar phases exhibit the Raman optical activity as a direct consequence of mirror symmetry breaking. Furthermore, we find that the Stokes and anti-Stokes spectra encode the time-reversal parity of the multipolar order, providing an all-optical means to distinguish multipolar phases. Our findings open a pathway for identifying multipolar orders in various materials through dual-circular Raman spectroscopy as a sensitive and versatile probe.