Cornell shows simple semiconductor films can break light front-back symmetry

Cornell University researchers report in Nature Materials that solution-processed semiconductor nanocluster films can absorb and emit linearly polarized light differently depending on which side faces the beam, breaking ordinary optical reciprocity without complex metamaterials or external magnetic fields. Materials science professor Richard Robinson and doctoral student Thomas Ugras studied magic-size clusters that self-assemble into spiral structures and form thin films with strong linear and chiral dichroism. Ugras linked those comparable effects mathematically to a directional asymmetry that prior work often dismissed as too small to see. The team demonstrated the effect in cadmium sulfide, cadmium selenide, and cadmium telluride films and pointed to uses such as nonreciprocal image generation and compact photonic devices. Phys.org summarized the Cornell Engineering release (DOI 10.1038/s41563-026-02660-0).