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

Abstract

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.

Keywords

• chirality
• magneto‐optics
• moiré metasurface
• nonreciprocity
• terahertz