Terahertz Spin-Conjugate Symmetry Breaking for Nonreciprocal Chirality and One-Way Transmission Based on Magneto-Optical Moiré Metasurface

Abstract

In this work, the gyrotropic semiconductor InSb into the twisted bilayer metasurface to form a magneto-optical moiré metasurface is introduced. Through the theoretical analysis, the “moiré angle” is developed in which case the nonreciprocity and chirality with the spin-conjugate asymmetric transmission are obtained due to the simultaneous breaking of both time-reversal symmetry and spatial mirror symmetry. The experiments confirm that the chirality can be actively manipulated by rotating the twisted angle and the external magnetic field, realizing spin-conjugate asymmetric transmission. Meanwhile, the two spin states also realize the nonreciprocal one-way transmission, and their isolation spectra are also spin-conjugate asymmetric: one is enhanced up to 48 dB, and the other's bandwidth is widened to over 730 GHz. This spin-conjugate symmetry-breaking effect in the MOMM brings a combination of time-space asymmetric transmission, and it also provides a new scheme for the implementation of high-performance THz chirality controllers and isolators.