Molecular Design for the Development of Organic Superconductors with Two-dimensional Electronic Structure

本计画的目的是发展具有二维电子结构的有机超导体的分子设计，并控制电子结构的维度。我们的策略是在平行于分子平面的方向上形成平坦的分子表面。基于这一思路，我们对BEDT-TSeF（BETS）、BMDT-TTF、ETIT、DMET-TSeF、TMET-STF等几种有机给体进行了研究，其中BETS、BMDT-TTF、ETIT提供了大量的低至4.2K稳定的二维金属，证实了我们分子设计的适用性。同构盐（TMET-STF）_2X（X=ClO_4，BF_4）具有一种新颖的晶体结构，它由两种类型的给体柱组成：一种是一维的，另一种是二维的。阳离子自由基盐（DMET-TSeF）_2X具有准一维电子结构。X=AuI_2和I_3的盐是常压超导体。在X=AuI_2，AuBr_2和AuCl_2的情况下，观察到了场致自旋密度波（FISDW）态。这些是第一个FISDW状态在有机系统以外的TMTSF家庭。

The purpose of this project is to develop the molecular design for the organic superconductor with two-dimensional electronic structure and for the control of the dimensionality of the electronic structure. Our strategy is to form a flat molecular surface in the direction parallel to the molecular plane. On the basis of this idea, we have studied several organic donors, BEDT-TSeF (BETS), BMDT-TTF, ETIT, DMET-TSeF, TMET-STF and so on. Among them, BETS, BMDT-TTF, and ETIT provided a lot of tow-dimensional metals stable down to 4.2 K, which have confirmed the applicability of our molecular design. The isostructural salts (TMET-STF)_2X (X=ClO_4, BF_4) have a novel crystal structure, which consists of two types of donor columns ; the one is one-dimensional and the other is two-dimensional. Cation radical salts (DMET-TSeF)_2X have quasi one-dimensional electronic structure. The salts with X=AuI_2 and I_3, were found to be ambient pressure superconductors. In the case of X=AuI_2, AuBr_2, and AuC1_2, the field induced spin density wave (FISDW) states were observed. These are the first FISDW states in organic systems other than the TMTSF family.