The Extended Coupled Cluster Treatment of Correlations in Quantum Magnets

Abstract

The spin-half XXZ model on the linear chain and the square lattice are examined with the extended coupled cluster method (ECCM) of quantum many-body theory. We are able to describe both the Ising-Heisenberg phase and the XY-Heisenberg phase, starting from known wave functions in the Ising limit and at the phase transition point between the XY-Heisenberg and ferromagnetic phases, respectively, and by systematically incorporating correlations on top of them. The ECCM yields good numerical results via a diagrammatic approach, which makes the numerical implementation of higher-order truncation schemes feasible. In particular, the best non-extrapolated coupled cluster result for the sublattice magnetization is obtained, which indicates the employment of an improved wave function. Furthermore, the ECCM finds the expected qualitatively different behaviours of the linear chain and the square lattice cases.

22 pages, 3 tables, and 15 figures

References in corpus (2)

• A Coupled-Cluster Formulation of Hamiltonian Lattice Field Theory: The Non-Linear Sigma Model
• Coupled Cluster Treatment of the XY model

Cited by in corpus (7)

• High-Order Coupled Cluster Method Calculations for the Ground- and Excited-State Properties of the Spin-Half XXZ Model
• Coupled Cluster Method Calculations Of Quantum Magnets With Spins Of General Spin Quantum Number
• High-Order Coupled Cluster Method (CCM) Calculations for Quantum Magnets with Valence-Bond Ground States
• Effect of anisotropy on the ground-state magnetic ordering of the spin-one quantum $J_1^{XXZ}$--$J_2^{XXZ}$ model on the square lattice
• Ab Initio Treatments of the Ising Model in a Transverse Field
• Phase transition in the transverse Ising model using the extended coupled-cluster method
• Thermal coupled cluster theory for SU(2) systems