Spin waves and renormalized magnetization in single and weakly coupled honeycomb layers

Abstract

We discuss the magnetic properties of the Hubbard model in honeycomb lattice layers. A ground state magnetic phase diagram is obtained as a function of interaction, U, and electron density, n. We also calculate the spin wave excitations in the antiferromagnetic insulating phase of single- and double-layered systems within Hartree–Fock-RPA theory. We also study the spin fluctuation correction to the mean field magnetization by virtual emission/absorption of spin waves. In the large U limit, this renormalization of magnetization is not so strong as that predicted by the Holstein–Primakoff theory of the Heisenberg antiferromagnet. The second neighbor hopping in the lattice has an important effect on the fluctuation correction to the magnetization although it has no effect on the mean field result.