Supersolidity in the Triangular Lattice Spin-1/2 XXZ Model: A Variational Perspective

We study the spin-1/2 XXZ model on the triangular lattice with a nearest neighbor anti ferromagnetic Ising coupling J(z) > 0 and unfrustrated (J(perpendicular to) < 0) or frustrated (J(perpendicular to) > 0) kinetic terms in a zero magnetic field. Incorporating long-range Jastrow correlations over a mean-field spin state, we obtain the variational phase diagram of this model on large lattices for arbitrary J(z) and either sign of J(perpendicular to). For J(perpendicular to) < 0, we find a root 3 X root 3 supersolid for J(z)/vertical bar J(perpendicular to)vertical bar greater than or similar to 4.7, in excellent agreement with quantum Monte Carlo data. For J(perpendicular to) > 0, a distinct root 3 X root 3 supersolid is found to emerge for J(z)/J(perpendicular to) >= 1. Both supersolids exhibit a spontaneous density deviation from half-filling. At J(z)/J(perpendicular to) = infinity, the crystalline order parameters of these two supersolids are nearly identical, consistent with exact results.