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Roles of Transition Metal d-Electrons in Electronic Properties of Organic Low-Dimensional Conductors

过渡金属d电子在有机低维导体电子性质中的作用

基本信息

批准号：
02452035
负责人：
KAGOSHIMA Seiichi
金额：
$ 3.39万
依托单位：
University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1990
资助国家：
日本
起止时间：
1990 至 1992
项目状态：
已结题

项目摘要

The purpose of the present study is to clarify roles of transition metal delectrons in electronic properties of organic low-dimensional conductors having transition metal ions. The experimental research was focused to investigation of properties of conduction electrons predominantly in DCNQI-Cu salts. In dmit salts characterization of electronic properties was made. Special effort was made in studying electronic properties near the reentrance transition of (DMeDCNQI)_2Cu.The followings are important results obtained in the present work: (1) The average valence of the copper ion in DCNQI-Cu slats was verified experimentally to be +4/3. (3) The magnetic structure of the anti-ferromagnetic state below about 8 K was made clear in the insulating state of DCNQI-Cu salts having the three-fold structure along the c-axis. (4) The reentrance transition in DMeDCNQI-Cu salt is accompanied with anomalies in the magnetic susceptibility, the three-fold structure, and the distortion around the copper ion. (5) Near the reentrance transition of DCNQI-Cu salts properties characteristic of the insulating state are present already in the metallic state. Furthermore magnetic fields as low as 10 T stabilize the insulating state. (6) In dmit salts both electron- and hole-like superconductivities were found. In addition both one- and two-dimensional properties were found depending on species of the metal ion.We clarified that the electronic state of DCNQI-Cu salts is described in terms of the Peierls instability in the one-dimensional band formed by pi electrons of DCNQI, the Mott transition of the band formed predominantly by the d-electrons of copper ions, the Jahn-Teller effect of copper ions, and electronphonon interactions in the "soft" lattice. It is remained unsolved to reveal microscopic mechanisms of the reentrance transition.

本研究的目的是阐明过渡金属电子在具有过渡金属离子的有机低维导体的电子性质中的作用。实验研究的重点是研究主要在 DCNQI-Cu 盐中的传导电子的性质。在dmit盐中进行了电子特性的表征。特别致力于研究(DMeDCNQI)_2Cu重入跃迁附近的电子性质。本工作取得了以下重要成果：(1)实验验证了DCNQI-Cu板条中铜离子的平均价态为+4/3。 (3)在具有沿c轴的三重结构的DCNQI-Cu盐的绝缘状态下，清楚了约8K以下的反铁磁状态的磁结构。 (4)DMeDCNQI-Cu盐中的重入转变伴随着磁化率、三重结构和铜离子周围畸变的异常。 (5)接近DCNQI-Cu盐的重入转变，绝缘态的特性特征已经以金属态存在。此外，低至 10 T 的磁场可以稳定绝缘状态。 (6) 在 dmit 盐中发现了类电子超导性和类空穴超导性。此外，根据金属离子的种类，还发现了一维和二维性质。我们阐明了 DCNQI-Cu 盐的电子态是用 DCNQI 的 pi 电子形成的一维带中的 Peierls 不稳定性、主要由铜离子的 d 电子形成的带的 Mott 跃迁、铜的 Jahn-Teller 效应来描述的 “软”晶格中的离子和电子声子相互作用。揭示折返转变的微观机制仍然悬而未决。