Electron Spin Resonance in Sine-Gordon Spin Chains in the Perturbative Spinon Regime

We report the low-temperature multifrequency ESR studies of copper pyrimidine dinitrate, a spin-$\frac{1}{2}$ antiferromagnetic chain with alternating $g$ tensor and the Dzyaloshinskii-Moriya interaction, allowing us to test a new theoretical concept proposed recently by Oshikawa and Affleck [Phys. Rev. Lett. 82, 5136 (1999)]. Their theory, based on bosonization and self-energy formalism, can be applied for precise calculation of ESR parameters of $S=\frac{1}{2}$ antiferromagnetic chains in the perturbative spinon regime. Excellent quantitative agreement between the theoretical predictions and experiment is obtained.

Figure 1

The ESR transmission spectra of Cu-PM taken at a frequency of 184 GHz at four different temperatures.

Figure 2

The temperature dependence of the ESR linewidth in Cu-PM at frequencies of 184, 93.1, and 9.4 GHz. Symbols denote the experimental results, and solid lines correspond to the best global fit using Eq. (2).

Figure 3

The field dependence of the ESR linewidth in Cu-PM at $T=10.3\mathrm{K}$. The solid line corresponds to Eq. (2) with the parameters obtained from the fit as described in the text.

Figure 4

The temperature dependence of the effective $g$ factor in Cu-PM for a frequency of 184 GHz. The solid line corresponds to Eq. (4) with the parameters obtained from the linewidth fit as described in the text.