Layer Dependent Spin Properties in InSe*

All-optical spin control enabled by optical spin selection rules offers chances for high speed spin orientation and manipulation. Although materials such as low-dimensional semiconductors have been extensively studied for spintronic applications, layered 2D materials offer novelty such as valleytronics and layer-dependent spin properties. InSe, a van der Waals material, has high electron mobility as well as predictions for optical spin selection rules, suggesting potential for 2D spintronics. Here we present layer-dependent optical-spin properties in InSe down to a few-layers. Optical orientation and Zeeman splitting contributions to polarization were identified separately in polarized photoluminescence. Time-resolved Kerr rotation revealed spin dynamics in multilayers. These results establish potential for orientation and manipulation of spin in InSe, opening the door for combining layer-dependent spin and favorable electronic properties in 2D materials.