Chiral Spin-Density Wave, Spin-Charge-Chern Liquid, and d plus id Superconductivity in 1/4-Doped Correlated Electronic Systems on the Honeycomb Lattice

Recently, two interesting candidate quantum phases-the chiral spin-density wave state featuring anomalous quantum Hall effect and the d + id superconductor-were proposed for the Hubbard model on the honeycomb lattice at 1/4 doping. Using a combination of exact diagonalization, density matrix renormalization group, the variational Monte Carlo method, and quantum field theories, we study the quantum phase diagrams of both the Hubbard model and the t-J model on the honeycomb lattice at 1/4 doping. The main advantage of our approach is the use of symmetry quantum numbers of ground-state wave functions on finite-size systems (up to 32 sites) to sharply distinguish different quantum phases. Our results show that for 1 less than or similar to U/t < 40 in the Hubbard model and for 0.1 < J/t < 0.80(2) in the t-J model, the quantum ground state is either a chiral spin-density wave state or a spin-charge-Chern liquid, but not a d + id superconductor. However, in the t-J model, upon increasing J, the system goes through a first-order phase transition at J/t 0.80(2) into the d + id superconductor. Here, the spin-charge-Chern liquid state is a new type of topologically ordered quantum phase with Abelian anyons and fractionalized excitations. Experimental signatures of these quantum phases, such as tunneling conductance, are calculated. These results are discussed in the context of 1/4-doped graphene systems and other correlated electronic materials on the honeycomb lattice.