Supersolidity in the triangular lattice spin-1/2 XXZ model: A variational perspective

TL;DR

This study uses a variational approach with long-range correlations to map the phase diagram of the spin-1/2 XXZ model on a triangular lattice, revealing supersolid phases consistent with quantum Monte Carlo results.

Contribution

It introduces a variational method incorporating long-range Jastrow correlations to accurately determine the phase diagram of the triangular lattice XXZ model for various parameters.

Findings

Identification of a $rac{ ext{sqrt}3} imesrac{ ext{sqrt}3}$ supersolid phase for $J_ot<0$ at high $J_z/|J_ot|$

Discovery of a distinct supersolid phase for $J_ot>0$ at $J_z/J_ot extgreater= 1$

Supersolids exhibit spontaneous density deviations from half-filling, with similar crystalline order parameters at large $J_z/J_ot$

Abstract

We study the spin-1/2 XXZ model on the triangular lattice with a nearest neighbor antiferromagnetic Ising coupling $J_z>0$ and unfrustrated ($J_\perp<0$) or frustrated ($J_\perp>0$) kinetic terms in 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 $J_\perp$. For $J_\perp<0$, we find a $\sqrt{3}\times\sqrt{3}$ supersolid for $J_z/|J_\perp| \gtrsim 4.7$, in excellent agreement with quantum Monte Carlo data. For $J_\perp >0$, a distinct $\sqrt{3}\times\sqrt{3}$ supersolid is found to emerge for $J_z/J_\perp \geq 1$. Both supersolids exhibit a spontaneous density deviation from half-filling. At $J_z/J_\perp=\infty$, the crystalline order parameters of these two supersolids are nearly identical, consistent with exact results.