Cluster Density Matrix Embedding Theory for Quantum Spin Systems

TL;DR

This paper introduces a modified cluster density matrix embedding theory applied to 2D quantum spin systems, accurately predicting ground-state energies and phase boundaries while being computationally efficient for entropy calculations.

Contribution

The paper develops a cost-effective cluster density matrix embedding approach tailored for quantum spin systems, with modifications enhancing accuracy and efficiency.

Findings

Accurately predicts ground-state energies and phase boundaries.

Agrees well with quantum Monte Carlo and coupled cluster results.

Efficiently computes von Neumann entropy related to quantum phase transitions.

Abstract

We applied cluster density matrix embedding theory, with some modifications, to a spin lattice system. The reduced density matrix of the impurity cluster is embedded in the bath states, which are a set of block-product states. The ground state of the impurity model is formulated using a variational wave function. We tested this theory in a two-dimensional (2-D) spin-1/2 J1-J2 model for a square lattice. The ground-state energy (GSE) and the location of the phase boundaries agree well with the most accurate previous results obtained using the quantum Monte Carlo and coupled cluster methods. Moreover, this cluster density matrix embedding theory is cost-effective and convenient for calculating the von Neumann entropy, which is related to the quantum phase transition.