Fellows,
I have been investigating graphene for a while, having finished a draft of my thesis paper on its band structure and how it can be modulated by atomic interactions.
When I read a recent Nature article, titled 'Quantum Spin Liquid emerging in two-dimensional correlated Dirac fermions' by Meng et al., I noted that their lattice was hexagonal, much like graphene. This inspired me to try spin polarization on graphene, even though I had done calculations without using it. As graphene has an even number of electrons in its orbitals, which are multiply-fold degenerate at K, we have configurations that can have fully paired up electrons in these states. At K, the eigenstates are four-fold degenerate (two pairs of degenerate states, with different dispersion), meaning that we have four separate states to occupy with four of the eight available electrons for graphene.
This brings me to the question: What would be the effects of spin polarization on such a system? How would the spin pairings be treated in it (unpolarized or polarized)? I have observed slight differences at K when doing a spin-polarized calculation with initial spin set at zero.