Low-energy singlet excitations in spin- 1/2 Heisenberg antiferromagnet on square lattice

Abstract

We present an approach based on a dimer expansion which describes low-energy singlet excitations (singlons) in spin-$\frac{1}{2}$ Heisenberg antiferromagnet on simple square lattice. An operator ("effective Hamiltonian") is constructed whose eigenvalues give the singlon spectrum. The "effective Hamiltonian" looks like a Hamiltonian of a spin-$\frac{1}{2}$ magnet in strong external magnetic field and it has a gapped spectrum. It is found that singlet states lie above triplet ones (magnons) in the whole Brillouin zone except in the vicinity of the point $(\pi ,0)$, where their energies are slightly smaller. Based on this finding, we suggest that a magnon decay is possible near $(\pi ,0)$ into another magnon and a singlon which may contribute to the dip of the magnon spectrum near $(\pi ,0)$ and reduce the magnon lifetime. It is pointed out that the singlon-magnon continuum may contribute to the continuum of excitations observed recently near $(\pi ,0)$.

References in corpus (15)

• Fractional excitations in the square-lattice quantum antiferromagnet
• Anomalous High-Energy Spin Excitations in La2CuO4
• Ground-state phases of the spin-1/2 J_1-J_2 Heisenberg antiferromagnet on the square lattice: A high-order coupled cluster treatment
• From Useful Algorithms for Slowly Convergent Series to Physical Predictions Based on Divergent Perturbative Expansions
• Spin excitations in a single La${}_2$CuO${}_4$ layer
• Quantum dynamics and entanglement of spins on a square lattice
• High-energy magnon dispersion and multi-magnon continuum in the two-dimensional Heisenberg antiferromagnet
• Nature of Spin Excitations in Two-dimensional Mott Insulators: Undoped Cuprates and Other Materials
• A Plane of Weakly Coupled Heisenberg Chains: Theoretical Arguments and Numerical Calculations
• Further Series Studies of the Spin-1/2 Heisenberg Antiferromagnet at T=0: Magnon Dispersion and Structure Factors
• The spin-1/2 square-lattice J_1-J_2 model: The spin-gap issue
• Spin-Wave Theory and Finite-Size Scaling for the Heisenberg Antiferromagnet
• Confinement and Deconfinement of Spinons in Two Dimensions
• Spectrum of short-wavelength magnons in two-dimensional quantum Heisenberg antiferromagnet on a square lattice: third order expansion in 1/S
• High-Energy Continuum of Magnetic Excitations in the Two-Dimensional Quantum Antiferromagnet Sr2CuO2Cl2

Cited by in corpus (4)

• Spin excitation spectra of the two dimensional $S=1/2$ Heisenberg model with a checkerboard structure
• Elementary excitations in the ordered phase of spin-1/2 J1-J2 model on square lattice
• Collective excitations in spin-1/2 magnets through bond-operator formalism designed both for paramagnetic and ordered phases
• Low-energy singlet sector in spin-$\frac{1}{2}$ $J_1$--$J_2$ Heisenberg model on square lattice