Roles of edge states in the specific heat and magnetic ordering of graphene strips

The role of edge states in the electronic specific heat and magnetic ordering of graphene strip is investigated by diagonalizing a lattice Hamiltonian for graphene strips. The magnetization of the edge sites is evaluated by employing the on-site Coulomb repulsion U within a mean-field approximation. We find that edge states give extra strong enhancement in the specific heat of zigzag strips at very low temperatures in addition to the Cel≃γTα behavior of two-dimensional (2D) massless fermions in graphene with View the MathML source and α≈2.27 at low temperatures. The onset value Uc for ferrimagnetic ordering in zigzag strips depends notably on the next nearest neighbour (NNN) hopping strength t2 but not much on the Rashba spin–orbit coupling VR for a given t2.