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Theoretical study on direct observation of electron spin resonance for spin gap

自旋间隙电子自旋共振直接观测的理论研究

基本信息

批准号：
13640371
负责人：
SAKAI Toru
金额：
$ 1.73万
依托单位：
Tohoku University (2002-2003)Tokyo Metropolitan Institute of Technology (2001)
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2001
资助国家：
日本
起止时间：
2001 至 2003
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-13640371/
关键词：
spin gap low-dimensional system quantum spin system strongly correlated electron system field-induced spin gap electron spin resonance 磁化プラトー強磁場スピンラダー高温超伝導

项目摘要

The electron spin resonance corresponding to the spin gap, which is one of the most interesting quantum phenomena in low-dimensional magnets, cannot be observed because of the spin conservation law. Recently, however, the direct transiti on of the spin gap was observed in some electron spin resonance measurements for the spin Pejeris material CeGeO_3 and Hakdane material NENP. In the present study, the mechanism of the direct transition was revealed and specified for these materials.As the origin of the direct transition, we proposed the effective staggered field induced by the alternating g-tensor and the Dzyaloshinski-Moriya interaction. In order to specify which of them, we introduced a selection rule of the electron spin resonance depending on the relative angle among the external field, crystal axes and rf-field of the incident micro wave : Comparing the selection rule and the experimental results, we concluded that the origin of the direct transition should be the effective staggered field for NENP, while both of the Dzyaloshinski-Moriya interaction and the staggered fieid for CuGeO_3.In addition we investigated some properties of the low-dimensional quantum systems like the spin gap system. For example, the field-induced spin gap due to the frustration of the antiferromagnetic interaction in the spin ladder, the field-induced spin liquid in the spin chain, the pseudogap induced by the spin fluctuation and the charge stripes due to the multispin exchange interaction in the high-Tc cuprate superconductors etc.

自旋能隙对应的电子自旋共振是低维磁体中最有趣的量子现象之一，但由于自旋守恒定律的限制，无法观测到。然而，最近在对自旋Pejeris材料CeGeO_3和Hake-GeO_3材料NENP的电子自旋共振测量中，观察到了自旋能隙的直接跃迁。在本研究中，我们揭示了这些材料的直接跃迁机制，并提出了由交替g张量和Dzyaloshinski-Moriya相互作用诱导的有效交错场作为直接跃迁的起源。为了说明它们中的哪一个，我们引入了电子自旋共振的选择规则，该规则取决于入射微波的外场、晶轴和射频场之间的相对角度：通过对选择定则和实验结果的比较，我们认为直接跃迁的起源应该是NENP的有效交错场，而对于CuGeO_3，则是Dzyaloshinski-Moriya相互作用和交错场。此外，我们还研究了低维量子系统如自旋能隙系统的一些性质。例如，在高Tc铜氧化物超导体中，由于反铁磁相互作用的阻挫而产生的场致自旋能隙，自旋链中的场致自旋液体，自旋涨落引起的赝能隙以及多自旋交换相互作用引起的电荷条纹等。