Phase diagram of the half-filled two-dimensional SU(N) Hubbard-Heisenberg model: A quantum Monte Carlo study (original) (raw)

We investigate the phase diagram of the half-filled SU (N ) Hubbard-Heisenberg model with hopping t, exchange J and Hubbard U , on a two-dimensional square lattice. In the large-N limit, and as a function of decreasing values of t/J, the model shows a transition from a d-density wave state to a spin dimerized insulator. A similar behavior is observed at N = 6 whereas at N = 2 a spin density wave insulating ground state is stabilized. The N = 4 model, has a d-density wave ground state at large values of t/J which as a function of decreasing values of t/J becomes unstable to an insulating state with no apparent lattice and spin broken symmetries. In this state, the staggered spin-spin correlations decay as a power-law, resulting in gapless spin excitations at q = (π, π). Furthermore, low lying spin modes with small spectral weight are apparent around the wave vectors q = (0, π) and q = (π, 0). This gapless spin liquid state is equally found in the SU (4) Heisenberg (U/t → ∞ ) model in the self-adjoint antisymmetric representation. An interpretation of this state in terms of a π-flux phase is offered. Our results stem from projective (T = 0) quantum Monte-Carlo simulations on lattice sizes ranging up to 24 × 24.

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