paper

Elementary excitations of S=1/2 one-dimensional antiferromagnet KCuGaF6 in magnetic field and quantum sine-Gordon model

arXiv:0902.1371 · doi:10.1103/PhysRevB.79.184401

Abstract

Elementary excitations of the S=1/2 one-dimensional Heisenberg antiferromagnet KCuGaF with exchange constant =103 K were investigated by high-frequency ESR measurements combined with a pulsed high magnetic field. When an external magnetic field H is applied in KCuGaF, a staggered magnetic field h is induced perpendicular to H owing to the staggered g tensor and the Dzyaloshinsky-Moriya (DM) interaction with an alternating D vector. Consequently, KCuGaF in a magnetic field is represented by the quantum sine-Gordon (SG) model. We observed many resonance modes including a soliton resonance, breathers, interbreather transitions and two-breather excitation. Their resonance conditions are beautifully described by the quantum SG field theory with one adjustable parameter . To investigate the relationship between the Curie term due to the DM interaction and the proportional coefficient , magnetic susceptibility measurements were also performed varying the external field direction.

9 pages, 6 figures

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