Quantum Moire exciton superlattices switch from opaque to transparent

A remarkably small adjustment to the stacking of two-dimensional materials can dramatically alter how they interact with light. Researchers at City University of Hong Kong and collaborating institutions demonstrate that a one-degree change in the twist angle of an atomically thin moiré system can switch its transmittance from nearly 0%, opaque, to approximately 1%, transparent. The work reveals that collective moiré exciton states exhibit radiative decay rates that are either strongly enhanced or suppressed depending on their in-plane wavevector, and that these states can be controlled with an applied electric field. This robust system offers a versatile platform for cooperative quantum optics, with potential for applications like single photon storage and switching. Calculations reveal that a moiré exciton lattice, a superlattice formed within layered two-dimensional materials, can switch between nearly complete opacity, a transmittance of approximately zero, and near-total transparency, a transmittance approaching one, with a 1∘ adjustment in the twist angle. This sensitivity stems from the cooperative optical response of the moiré excitons themselves, where collective behavior dictates how light interacts with the material. This duality arises from the precise arrangement of excitons within the…