Ground-state phase diagram of the quantum J1-J2 model on the honeycomb lattice

TL;DR

This study maps the ground-state phase diagram of the quantum J1-J2 model on a honeycomb lattice using an entangled-plaquette variational approach, revealing classical magnetic orders and a disordered intermediate phase.

Contribution

It introduces a variational ansatz to accurately determine the phase diagram of the J1-J2 model on the honeycomb lattice, highlighting the limitations of simplified Hubbard model reductions.

Findings

Classical Nèel order for J2/J1 less than ~0.2

Collinear order for J2/J1 greater than ~0.4

Disordered phase in the intermediate J2/J1 range

Abstract

We study the ground-state phase diagram of the quantum $J_1-J_2$ model on the honeycomb lattice by means of an entangled-plaquette variational ansatz. Values of energy and relevant order parameters are computed in the range $0\le {J_2}/{J_1} \le 1$. The system displays classical order for ${J_2}/{J_1}\lesssim 0.2$ (N\'eel), and for $J_2/J_1 \gtrsim 0.4$ (collinear). In the intermediate region, the ground-state is disordered. Our results show that the reduction of the half-filled Hubbard model to the model studied here does not yield accurate predictions.