Coexistence of the bond-order wave and antiferromagnetism in a two-dimensional half-filled Peierls-Hubbard model

The two-dimensional Peierls-Hubbard model is studied at half filling within both Hartree-Fock and Kotliar-Ruckenstein slave-boson theory. The interplay between two types, of long-range order, bond-order wave (BOW) and antiferromagnetism (AFM), is analyzed for two representative dimerization patterns, corresponding both to the same wave vector (pi,pi). For each pattern, the Peierls dimerization (and associated BOW) is weakened and finally suppressed with increasing Hubbard on-site. interaction, and correspondingly AFM is gradually enhanced. In particular, a coexistence regime with both BOW and AFM order is established in the parameter space of electron-lattice and Hubbard interactions.