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 language | English |
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Article number | 094419 |
Journal | Physical Review B - Condensed Matter and Materials Physics |
Volume | 90 |
Issue number | 9 |
DOIs | |
State | Published - Sep 29 2014 |