In 2005 Novoselov and coworkers [1] reported on strictly two-dimensional (2D) materials, which can be viewed as single atomic planes pulled out of bulk crystals. These atomically thin sheets are stable under ambient conditions, exhibit a high crystal quality, and are continuous on a macroscopic scale. They can be conductors (graphene), semiconductors (transition-metal dichalcogenides), or insulators (hBN). Their properties are significantly different from those of the three-dimensional precursor. This is true from a thermodynamic point of view and it becomes impressive when we consider electronic and optical properties [2]. For this reason, they have promise for a large number of applications such as new direct band gap materials (like the monolayer MoS2) in photonics or the thinnest possible circuits in micro-electronics.

In our group, the activities in this area concern: 1) the connection in between the microscopic and the macroscopic optical description of a 2D crystal; 2) linear and non-linear optical experiments; 3) the interaction of a light beam with a 2D crystal; 4) the study of multilayer structures up to a thickness where the bulk susceptibility is found.

1. K. Novoselov, D. Jiang, F. Schedin, T. Booth, V. Khotkevich, S. Morozov, and A. Geim, Two-dimensional atomic crystals, Proc. Natl. Acad. Sci. USA 102, 10451 (2005). 

2. J. D. Elliott, Z. Xu, P. Umari, G. Jayaswal, M. Chen, X. Zhang, A. Martucci, M. Marsili, and M. Merano, Surface susceptibility and conductivity of MoS2 and WSe2 monolayers: A first-principles and ellipsometry characterization, Phys. Rev. B 101, 045414 (2020).