The connection between chirality and electromagnetism has attracted much attention through the recent history of science, allowing the discovery of crucial nonreciprocal optical phenomena within the context of fundamental interactions between matter and light. A major phenomenon within this family is the so-called Faraday chiral anisotropy, the long-predicted but yet unobserved effect which arises due to the correlated coaction of both natural and magnetically induced optical activities at concurring wavelengths in chiral systems. Here, we report on the detection of the elusive anisotropic Faraday chiral phenomenon and demonstrate its enantioselectivity. The existence of this fundamental effect reveals the accomplishment of envisioned nonreciprocal electromagnetic metamaterials referred to as Faraday chiral media, systems where novel electromagnetic phenomena such as negative refraction of light at tunable wavelengths or even negative reflection can be realized. From a more comprehensive perspective, our findings have profound implications for the general understanding of parity-violating photon-particle interactions in magnetized media.
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The authors thank A. Gevorgyan for useful discussions and the Advanced Microscopy Laboratory, CRANN, TCD for assistance during sample preparation. This work was supported by the following grants: Science Foundation Ireland PI-Grant 08/IN.1/I1873; CSET 08/CE/I1432; European Union EuroMagNET II Programme; Cycle 4 of the Programme for Research in Third-Level Institutions (PRTLI4) Ireland; Programme Investissements d’Avenir under the program ANR-11-IDEX-0002-02, ref. ANR-10-LABX-0037-NEXT; Vinnova (Project ID: 2019-02878); the MINECO Ramón y Cajal program (No. RYC2019-028443-I); the Center for Nanostructured Graphene (Danish National Research Foundation, Project No. DNRF103); VILLUM FONDEN (Grant No. 16498); 2020 funding and HPC Centre at SDU; the Operational Competitivness and Internationalization Programme, COMPETE 2020 (Project No. POCI-01-0247-FEDER-39479); the Portugese Foundation for Science and Technology, FCT (Project No. FCT-UID/FIS/04650/2020) and the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) -- Project-ID 429529648 -TRR 306 QuCoLiMa (“Quantum Cooperativity of Light and Matter”).