Terahertz Circular Dichroism in Chiral Perovskites

Chiral organic-inorganic hybrid perovskites (OIHPs) have been extensively studied to find tunable chiroptical responses in the visible range. Further exploitation of chiral OIHPs beyond the narrow visible range of wavelengths is hampered by an incomplete understanding of the magnitude and structure-property relations for other parts of the electromagnetic spectrum. The difficulties with experimental observation and insufficient experimental base for photons with energy less than 1eV also limited exploratory activities for chiroptical effects in the far-infrared part of the spectrum. Here, we demonstrated the first observations of strong chiral phonons with ellipticity reaching –9.17 deg. The chiral phonon modes arise from lattice chirality in chiral OIHPs, as revealed by terahertz circular dichroism spectroscopy. Our findings provide clues for the design of chiral OIHPs and open the door for utilizing chiroptical effects in the terahertz area essential for sensing and telecommunication.