Ground-State Properties of Quantum Many-Body Systems: Entangled-Plaquette States and Variational Monte Carlo

TL;DR

This paper introduces a novel variational ansatz using entangled-plaquette states for ground-state calculations in quantum many-body lattice systems, demonstrating high accuracy across various models including frustrated systems.

Contribution

The paper presents a new entangled-plaquette variational ansatz that is applicable in any dimension and effectively handles sign problems, improving ground-state estimates for complex lattice models.

Findings

Accurate ground-state energies for 2D spin models, including frustrated systems.

Good agreement with exact results for unfrustrated models.

Favorable comparison with existing variational methods for frustrated systems.

Abstract

We propose a new ansatz for the ground-state wave function of quantum many-body systems on a lattice. The key idea is to cover the lattice with plaquettes and obtain a state whose configurational weights can be optimized by means of a Variational Monte Carlo algorithm. Such a scheme applies to any dimension, without any "sign" instability. We show results for various two dimensional spin models (including frustrated ones). A detailed comparison with available exact results, as well as with variational methods based on different ansatzs is offered. In particular, our numerical estimates are in quite good agreement with exact ones for unfrustrated systems, and compare favorably to other methods for frustrated ones.