On the dynamics of coupled S=1/2 antiferromagnetic zig-zag chains

Abstract

We investigate the elementary excitations of quasi one-dimensional S=1/2 systems built up from zig-zag chains with general isotropic exchange constants, using exact (Lanczos) diagonalization for 24 spins and series expansions starting from the decoupled dimer limit. For the ideal one-dimensional zig-zag chain we discuss the systematic variation of the basic (magnon) triplet excitation with general exchange parameters and in particular the presence of practically flat dispersions in certain regions of phase space. We extend the dimer expansion in order to include the effects of 3D interactions on the spectra of weakly interacting zig-zag chains. In an application to KCuCl_3 we show that this approach allows to determine the exchange interactions between individual pairs of spins from the spectra as determined in recent neutron scattering experiments.

8 pages, 9 figures; some changes, figure added; final version

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• Pressure-Induced Magnetic Quantum Phase Transition in Gapped Spin System KCuCl3
• A switchable controlled-NOT gate in a spin-chain NMR quantum computer
• Magnon decay in gapped quantum spin systems
• Softening of Magnetic Excitations Leading to Pressure-Induced Quantum Phase Transition in Gapped Spin System KCuCl${}_3$
• Comparative study between two quantum spin systems KCuCl${}_3$ and TlCuCl${}_3$
• Dynamical Structure Factors for Dimerized Spin Systems
• Magnon-mediated NMR quantum gates in a 1-D antiferromagnet
• New results for the t-J model in ladders: Changes in the spin liquid state with applied magnetic field. Implications for the cuprates
• Magnetization process in a frustrated plaquette dimerized ladder
• Spin excitations in the two-dimensional strongly coupled dimer system malachite
• Single hole doped strongly correlated ladder with a static impurity
• One-dimensional physics of the frustrated quantum magnet PHCC