Gauge theory of the Hubbard model on honeycomb lattice and its instanton effect

Understand

In this paper we investigate possible spin disordered phase in the Hubbard model on the honeycomb lattice.

• Using a slave-particle theory that include the charge fluctuations, we find a meanfield spin disordered phase in a range of on-site repulsion $U$.
• The spin disordered state is described by gapped fermions coupled to compact U(1) gauge field.
• We study the confinement/deconfinement problem of the U(1) gauge theory due to the instantons proliferation.