Quantum disorder due to singlet formation: The Plaquette lattice

Abstract

I study the order/disorder transition due to singlet formation in a quantum spin system by means of exact diagonalization. The systems is build by spin 1/2 on a two-dimensional square lattice with two different kinds of antiferromagnetic Heisenberg interactions. The interaction J_p connects 4 nearest neighbor spins on a plaquette. The interaction J_n connects the plaquettes with each other. If J_p=J_n the systems reduces to the simple square lattice case. If one of the interactions becomes sufficiently larger then the other the purely quantum effect of singlet formation drives the system into a disordered phase with only short range correlations in the plaquettes and a spin gap. I study the transition point by evaluating the spin gap and spin-spin correlations. I compare the results with previously calculated data from a non-linear sigma model approach, spin wave theory and series expansion calculations. I confirm a critical value of J_n \approx 0.6 for the quantum phase transition point.

5 pages (Revtex), 7 figures

References in corpus (6)

• Dimer Order with Striped Correlations in the J_1-J_2 Heisenberg Model
• Magneto-thermodynamics of the spin-1/2 Kagome antiferromagnet
• Ground State and Elementary Excitations of the S=1 Kagome Heisenberg Antiferromagnet
• Two-Dimensional Quantum Spin Systems with Ladder and Plaquette Structure
• Quantum Phase Transitions in Two-Dimensional Spin Systems with Ladder, Plaquette and Mixed-Spin Structures
• Exact diagonalization of the S=1/2 Heisenberg antiferromagnet on finite bcc lattices to estimate properties on the infinite lattice

Cited by in corpus (10)

• Nonlinear Sigma model method for the J1-J2 Heisenberg model: disordered ground state with plaquette symmetry
• Numerical Contractor Renormalization Method for Quantum Spin Models
• Quantum Phase Transition in a Heisenberg Antiferromagnet on a Square Lattice with Strong Plaquette Interactions
• A renormalized excitonic method in terms of block excitations. Application to spin lattices
• On the valence-bond solid phase of the crossed-chain quantum spin model
• Spin excitation spectra of the two dimensional $S=1/2$ Heisenberg model with a checkerboard structure
• Ground-state phase diagram of the spin-1/2 square-lattice J1-J2 model with plaquette structure
• Collective excitations in spin-1/2 magnets through bond-operator formalism designed both for paramagnetic and ordered phases
• Structural and magnetic instabilities of layered magnetic systems
• Quantum phase transition in the Plaquette lattice with anisotropic spin exchange