Magnons and continua in a magnetized and dimerized spin- 12 chain

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

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9 Scopus citations

Abstract

We examine the magnetic field dependent excitations of the dimerized spin-1/2 chain, copper nitrate, with antiferromagnetic intradimer exchange J1=0.44(1)meV and exchange alternation α=J2/J1=0.26(2). 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 magnonlike modes, respectively. The number of modes and the antiphase relationship between the wave-vector dependent energy and intensity of magnon scattering reflect the distinct ground states: A singlet ground state at low fields μ0H<μ0Hc1=2.8T and an Sz=1/2 product state at high fields μ0H>μ0Hc2=4.2T. In the intermediate-field regime, a continuum of scattering for â.,ω≈J1 is indicative of a strongly correlated gapless quantum state without coherent magnons.

Original languageEnglish
Article number094419
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume90
Issue number9
DOIs
StatePublished - Sep 29 2014

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