Poisson's ratio in layered two-dimensional crystals

We present first-principles calculations of elastic properties of multilayered two-dimensional crystals, such as graphene, h-BN, and 2H-MoS2, which show that their Poisson's ratios along the out-of-plane direction are negative, near zero, and positive, respectively, spanning all possibilities for the sign of the ratios. While the in-plane Poisson's ratios are all positive regardless of their disparate electronic and structural properties, the characteristic interlayer interactions as well as layer stacking structures are shown to determine the sign of their out-of-plane ratios. A thorough investigation of elastic properties as a function of the number of layers for each system is also provided, highlighting their intertwined nature between elastic and electronic properties.