Scalable One-Dimensional Excitons in a Van der Waals Magnet

The discovery of two-dimensional (2D) van der Waals magnets has greatly expanded our ability to create and control nanoscale phases. A unique capability appears when a 2D magnet is also a semiconductor, which features tightly bound excitons with large oscillator strengths and potential tunability with magnetic field. While crystalline and geometric anisotropy can lead to anisotropic 2D (black phosphorus) and even 1D excitons (carbon nanotube), the superior excitonic properties do not easily scale up with increasing layer number/system size. Here we report scalable 1D excitons in the 2D A-type antiferromagnetic semiconductor CrSBr from few-layer to the bulk limit. The 1D confinement originates from a combination of in-plane crystalline anisotropy and inter-plane magnetic anisotropy. Magnetic confinement of the 1D excitons is established through the layer dependence and temperature dependence of the exciton properties, and further corroborated with <i>ab initio</i> theory calculations. Our work establishes a novel avenue towards the large-scale application of emergent functionalities of low-dimensional materials.