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Size and temperature dependence of the line shape of ESR spectra of the XXZ antiferromagnetic chain

Phys. Rev. B 95, 024402

2017年1月4日(水)

Hiroki Ikeuchi, Hans De Raedt, Sylvain Bertaina, and Seiji Miyashita ( https://doi.org/10.1103/PhysRevB.95.024402 )

Abstract

The electron spin resonance spectrum of the XXZ spin chain with finite length shows a double-peak structure at high temperatures around the electron paramagnetic resonance (EPR) frequency. This fact has been pointed out by direct numerical methods [S. El Shawish, O. C´epas, and S. Miyashita, Phys. Rev. B 81, 224421 (2010);
H. Ikeuchi, H. De Raedt, S. Bertaina, and S. Miyashita, ibid. 92, 214431 (2015)]. The question of whether the double-peak structure survives in the thermodynamics is of particular interest.We study the size dependence of the line shape, including the even-odd effect. It is found that the peaks forming the double-peak structure are assigned to individual resonances, each of which is specified by the magnetizations of the resonating states (M,M − 1).
To understand dependences, we decompose the spectrum into contributions from transitions specified by the magnetization, and we characterize the structure of the spectrum by individual contributions. We analyze the size dependence of each contribution individually by extending the moment method introduced by M. Brockman
et al. to each component, and we find that the mean of each peak approaches the paramagnetic resonance point with 1/N (where N is the length of the chain), which indicates that the separation of the peaks of the double-peak structure also vanishes inversely with the system size.We also study the temperature dependence of the structure. At low temperatures, the spectrum has a single peak with a finite width at a position with a finite shift from the frequency of EPR, as pointed out by the analysis of field-theoretical works [M. Oshikawa and I. Affleck, Phys. Rev. Lett. 82, 5136 (1999)]. The study of the temperature dependence of the spectrum shows how the
high-temperature spectrum changes to the low-temperature one with a drastic broadening of the spectrum.

その他特記事項

The present work was supported by Grants-in-Aid for Scientific Research C (25400391) fromMinistry of Education, Culture, Sports, Science and Technology (MEXT) of Japan,
and the Elements Strategy Initiative Center for Magnetic Materials under the outsourcing project of MEXT. The numerical calculations were supported by the supercomputer center of Institute of Solid State Physics (ISSP) of Tokyo University.


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元素戦略拠点

触媒・電池元素戦略拠点
触媒・電池元素戦略研究拠点 (京都大学)
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東工大元素戦略拠点 (東京工業大学)
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構造材料元素戦略研究拠点 (京都大学)
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