Oral: Demonstration of Time-Reversal Symmetry Breaking in Chiral Terahertz Photonic-Crystal Cavities

Light-matter interactions in chiral cavities offer a promising approach to control material properties by breaking fundamental symmetries like time-reversal or inversion symmetry. To date, only a few demonstrations of chiral cavities exhibiting broken time-reversal breaking have been reported. These implementations typically require the application of a strong magnetic field or the hybridization of cavity modes with matter excitations in the ultrastrong coupling regime. Here, we present a one-dimensional terahertz photonic-crystal cavity in which time-reversal symmetry is broken. Our cavity consists of a high-resistivity silicon wafer sandwiched between lightly n-doped InSb wafers. By leveraging the nonreciprocal properties of a terahertz magnetoplasma and the low effective mass of electrons in InSb, we achieved a cavity mode with a single circular polarization at 0.67 THz in the presence of a small (~0.3 T) magnetic field, achieving a Quality factor exceeding 200. Temperature, magnetic field, and polarization-dependent experiments and simulations validate the proof-of-concept chiral cavity with broken time-reversal symmetry, making it well-suited for studies of chiral light-matter interactions in the terahertz range.