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Computation of ESR spectra from the time evolution of the magnetization: Comparison of autocorrelation and Wiener-Khinchin-relation-based methods

Phys. Rev. B 92, 214431

2015年12月21日(月)

doi:10.1103/PhysRevB.92.214431
Hiroki Ikeuchi, Hans De Raedt, Sylvain Bertaina, and Seiji Miyashita

Abstract

The calculation of finite temperature electron spin resonance (ESR) spectra for concrete specified crystal configurations is a very important issue in the study of quantum spin systems. Although direct evaluation of the Kubo formula by means of numerical diagonalization yields exact results, memory and CPU time restrictions limit the applicability of this approach to small system sizes. Methods based on the time evolution of a single pure quantum state can be used to study larger systems. One such method exploits the property that the expectation value of the autocorrelation function obtained for a few samples of so-called thermal typical states yields a good estimate of the thermal equilibrium value. In this paper, we propose a new method based on a Wiener-Khinchin-like theorem for quantum system. By comparison with exact diagonalization results, it is shown that both methods yield correct results. As the Wiener-Khinchin-based method involves sampling over thermal typical states, we study the statistical properties of the sampling distribution. Effects due to finite observation time are investigated and found to differ for the two methods but it is also found that, for both methods, the effects vanish as the system size increases. We present ESR spectra of the one-dimensional XXZ Heisenberg chain of up to 28 spins and discuss the dependence of separation of double peaks on the chain length.

その他特記事項

The present work was supported by Grants-in-Aid for Scientific Research C (25400391) from Ministry of Education, Culture, Sports, Science and Technology (MEXT) of Japan and the Elements Strategy Initiative Center forMagnetic 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.
We also acknowledge the JSPS Core-to-Core Program: Nonequilibrium dynamics of soft matter and information.


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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)
東工大元素戦略拠点
東工大元素戦略拠点 (東京工業大学)
構造材料元素戦略研究拠点
構造材料元素戦略研究拠点 (京都大学)
高効率モーター用磁性材料技術研究組合
高効率モーター用 磁性材料技術研究組合