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Dynamical spin correlations as imaged by inelastic neutron scattering are an important source of information about the nature of elementary excitations in quantum magnets. We report numerical results based on exact diagonalization exploring the diversity of response features. We briefly present three prototypical cases (S=1/2): i) The square lattice Heisenberg antiferromagnet, where there are well defined spin waves at low magnetic fields, which become unstable and decay into continua at high magnetic fields [1]. ii) Spin ladders in a magnetic field, where the coherent triplon fractionalizes into spinon continua as the spin gap is closed. Here we compare theoretical results with INS experiments performed on the Dpip ladder material [2]. And iii) the Heisenberg antiferromagnet on the kagome lattice, which is a highly frustrated quantum magnet with a magnetically disordered spin liquid ground state. The dynamical response is surprisingly broad with a characteristic increase towards low energies [3]. [1] A. Lüscher and A. Läuchli, The antiferromagnetic spin-1/2 Heisenberg model on the square lattice in a magnetic field, arxiv:0812.3420. [2] B. Thielemann et al., Direct Observation of Magnon Fractionalization in the Quantum Spin Ladder, arxiv:0812.3880. [3] A. Läuchli and C. Lhuillier, Dynamical Correlations of the Kagome S=1/2 Heisenberg Quantum Antiferromagnet, arxiv:0901.1065 |
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