paper

Electron Spin Resonance in S=1/2 antiferromagnetic chains

arXiv:cond-mat/0108424 · doi:10.1103/PhysRevB.65.134410

Abstract

A systematic field-theory approach to Electron Spin Resonance (ESR) in the quantum antiferromagnetic chain at low temperature (compared to the exchange coupling ) is developed. In particular, effects of a transverse staggered field and an exchange anisotropy (including a dipolar interaction) on the ESR lineshape are discussed. In the lowest order of perturbation theory, the linewidth is given as and , respectively. In the case of a transverse staggered field, the perturbative expansion diverges at lower temperature; non-perturbative effects at very low temperature are discussed using exact results on the sine-Gordon field theory. We also compare our field-theory results with the predictions of Kubo-Tomita theory for the high-temperature regime, and discuss the crossover between the two regimes. It is argued that a naive application of the standard Kubo-Tomita theory to the Dzyaloshinskii-Moriya interaction gives an incorrect result. A rigorous and exact identity on the polarization dependence is derived for certain class of anisotropy, and compared with the field-theory results.

53 pages in REVTEX, 7 figures in EPS included; revised version with missing references and corrections

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