Journal of the Physical Society of Japan
ESR in Antiferromagnetic Chains: a Field-Theory Approach
Masaki Oshikawa
Abstract
We review our recent field-theory approach to ESR in quantum spin chains at low temperature. The perturbative expansion in an anisotropy is formulated systematically, avoiding previously made assumptions. The linewidth is calculated in the lowest order of the perturbation theory for a transverse staggered field and an exhange anisotropy. In the case of the transverse staggered field, the perturbative expansion become divergent at lower temperature. The spectrum in the zero energy limit is discussed using non-perturbative exact results on the sine-Gordon field theory. These theoretical results are compared to experimental data, particularly those on Cu benzoate.