Magnetism in strained graphene dots

Abstract

We study the magnetization of square and hexagonal graphene dots. It is shown that two classes of hexagonal dots have a second order phase transition at a critical Hubbard energy $U$, whoose value is similar to the one in bulk graphene, albeit the dots do not have a density of states proportional to the absolute value of the energy, relatively to the Dirac point. Furthermore, we show that a particular class of hexagonal dots having zig-zag edges, does not exhibit zero energy edge states. We also study the effect of uniaxial strain on the evolution of the magnetization of square dots, and find that the overall effect is an enhancement of magnetization with strain. The enhancement can be as large as 100% for strain of the order of 20%. Additionaly, stress induces a spatial displacement of the magnetization over the dot, moving it from the zig-zag to the armchair edges.