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arXiv · 1406.7596

Magnons and continua in a magnetized and dimerized spin-1/2 chain

M. B. Stone·Y. Chen·D. H. Reich·C. Broholm·G. Xu·J. R. D. Copley·J. C. Cook
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Abstract

We examine the magnetic field dependent excitations of the dimerized spin-1/2 chain, copper nitrate, with antiferromagnetic intra-dimer exchange $J_1=0.44$ meV and exchange alternation $\alpha=J_2/J_1=0.24$. Magnetic excitations in three distinct regimes of magnetization are probed through inelastic neutron scattering at low temperatures. At low and high fields there are three and two long-lived magnon-like modes, respectively. The number of modes and the anti-phase relationship between the wave-vector dependent energy and intensity of magnon scattering reflect the distinct ground states: A singlet ground state at low fields $\mu_0H < \mu_0H_{c1} = 2.8$~T and an $S_z=1/2$ product state at high fields $\mu_0H > \mu_0H_{c2} = 4.2$~T. In the intermediate field regime, a continuum of scattering for $\hbar\omega\approx J_1$ is indicative of a strongly correlated gapless quantum state without coherent magnons.

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M. B. Stone, Y. Chen, D. H. Reich, C. Broholm, G. Xu, J. R. D. Copley, J. C. Cook. 2014-06-30. Magnons and continua in a magnetized and dimerized spin-1/2 chain. https://doi.org/10.1103/physrevb.90.094419

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