Physical properties of CrI3 and other van der Waals materials

Magnetic two-dimensional (2D) materials offer a promising platform for the miniaturization of nonreciprocal photonic components, potentially enabling compact, on-chip unidirectional light transport. However, the successful incorporation of these materials into photonic devices hinges on the accurate determination of their optical properties. We will start this talk discussing the interest in CrI3, a magnetic semiconductor with a layer structure, and the behavior of a few layers material. We have recently studied the optical properties of CrI3 as a function of the number of layers, observing two main transitions in the visible region. The transition energies change with the number of layers revealing three different regimes: nanoscopic, mesoscopic and bulk. We will explore the physics underlying these regimes using a phenomenological model and the crystal and electronic band structures obtained through density functional theory calculations. Additionally, we will discuss the relevance of other layered materials, such as BiI3 and NiBr2, and present some preliminary results.