Zeeman levels with exotic field dependence in the high field phase of an S=1 Heisenberg antiferromagnetic chain.
We have performed electron spin resonance measurements over a wide frequency and magnetic field range on a single crystal of the S=1 quasi-one-dimensional Heisenberg antiferromagnet Ni(C5H14N2)2N3(PF6). We observed gapped excitation branches above the critical field H(c) where the Haldane gap closes. These branches are analyzed by a phenomenological field theory using the complex-field phi(4) model. A satisfactory agreement between experiment and theory is obtained.
Hagiwara
M
M
RIKEN (The Institute of Physical and Chemical Research), Wako, Saitama 351-0198, Japan.
Honda
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Katsumata
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Kolezhuk
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Mikeska
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