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

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 ${\mu }_{0}H<{\mu }_0{H}_{c1}=2.8$~T and an $S_z=1/2$ product state at high fields ${\mu }_{0}H>{\mu }_0{H}_{c2}=4.2$~T. In the intermediate field regime, a continuum of scattering for $\hslash \omega \approx J_1$ is indicative of a strongly correlated gapless quantum state without coherent magnons.

15 pages, 13 figures

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• Bose-Einstein Condensation in Magnetic Insulators
• Dimensional reduction at a quantum critical point
• Thermodynamics of the Spin Luttinger-Liquid in a Model Ladder Material
• Field-driven phase transitions in a quasi-two-dimensional quantum antiferromagnet
• Critical properties and Bose Einstein Condensation in dimer spin systems
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• Magnetic Phase Diagram of Alternating Chain Compound Pb2V3O9

Cited by in corpus (2)

• Zero-temperature study of a tetrameric spin-$1/2$ chain in a transverse magnetic field
• Criticality-Enhanced Magnetocaloric Effect in Quantum Spin Chain Material Copper Nitrate