Talk given by

Prof.Kirill Bolotin

Department of Physics

Freie Universität Berlin


Abstract:

Two-dimensional materials (2DM) such as graphene, monolayer boron nitride, or monolayer molybdenum disulfide are crystalline layers only a few atoms thick. We examine the nanomechanical properties of these materials using newly developed techniques to pull, bend, twist, and cut them. In this talk, we will show that the mechanics of 2DMs is drastically different from that of “conventional” bulk matter. It will be demonstrated that inevitable out-of-plane crumpling modifies every mechanical property of 2DMs making their mechanical response more akin to that of biological membranes than of solid objects. For the case of a prototypical 2DM—graphene—it will be shown that out-of-plane crumpling renders the thermal expansion coefficient negative and substrate dependent, reduces the Young’s modulus, increases the bending rigidity by several orders of magnitude, and changes the sign of the Poisson ratio.