Metal-Insulator Transition and lattice vibrationon (DMe-DCNQI)_2Cu

(DMe-DCNQI)_2Cu 上的金属-绝缘体转变和晶格振动

基本信息

批准号：
11440118
负责人：
NISHIO Yutaka
金额：
$ 6.14万
依托单位：
Toho University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1999
资助国家：
日本
起止时间：
1999 至 2001
项目状态：
已结题

项目摘要

Metal complex salts (DMe-DCNQI)_2Cu exhibits a reentrant metal-insulator transition under delicate pressure. The mixing of DCNQIπ electron and Cu 3d electron located near Fermi level generates 3dFermi face and suppresses low dimensional instability. We carried out adeuteration of methyl group, a size of which can control the electronic dimensionality and tune the reentrant M-I transition.We have experimentally studied the mechanism of reentrant metal-insulator-metal transition of DCNQI-Cu system using this deuterated system. Measurements of specific heat and latent heat were carried out by thermal relaxation (0.5<T<40K), adiabatic pulse (20<T<100K) and Differential Thermal Analysis (DTA) methods on samples under various chemical pressures. From the experimental results, we determined the Gibbs free energy difference between metallic and insulating phases and succeeded to draw the phase diagram that reproduces the experimental result quite well. We conclude that the free energy change of free electrons (metallic phase) to localized electrons with spin 1/2 (insulating phase) is essential to drive the anomalous phase transition in this system. Contribution of lattice system is also clarified.In this deuterated system, we have discovered that an orientation freedom in a deuterated methyl group brings two kinds of anomalous specific heat todeuterated (DMe-DCNQI)_2Cu system. In system containing methyl groups with one deuterium atom (CH_2D), we found Schottky type of specific heat. In system with CHD_2, we observed peaks not of Schottky type. To find out an origin and mechanism of these anomalies, we carried out the thermal study of the mixed crystals composed ofCH_2D and CHD_2. We clarified the conformational ordering of CHD_2 molecular along c axis in the DCNQI-Cu system.

金属复合盐（DME-DCNQI）_2CU在微妙的压力下表现出重入的金属绝缘体过渡。位于费米水平附近的DCNQIπ电子和Cu 3D电子的混合产生了3Dfermi面，并抑制了低维不稳定。我们进行了甲基的封存，其中大小可以控制电子维度并调整重新进入M-1的过渡。我们已经通过使用这种剥离系统的DCNQI-CU系统进行了实验研究了重新进入金属绝缘体 - 金属转变的机制。通过热弛豫（0.5 <t <40k），绝热脉冲（20 <t <100k）以及各种化学压下样品的差分热分析（DTA）方法，对特定热和潜热的测量进行了测量。从实验结果中，我们确定了金属和绝缘阶段之间的Gibbs自由能差，并成功地绘制了该相。可以很好地重现实验结果的图。我们包括，自由电子（金属相）对具有自旋1/2（绝缘相）的局部电子的自由能变化对于驱动该系统中的异常相变至关重要。晶格系统的贡献也被阐明了。在这个一个申请的系统中，我们发现氘代甲基的方向自由带来了两种异常的特异性热todeutederated（DME-DCNQI）_2CU系统。在含有一个氘原子（CH_2D）的甲基的系统中，我们发现了Schottky类型的特定热量。在具有CHD_2的系统中，我们观察到不是Schottky类型的峰。为了找出这些异常的起源和机制，我们对由CH_2D和CHD_2组成的混合晶体进行了热研究。我们阐明了沿dcnqi-Cu系统中C轴的chd_2分子的构象顺序。

项目成果

期刊论文数量（97）

专著数量（0）

科研奖励数量（0）

会议论文数量（0）

专利数量（0）

H. Mori, T. Okano, S. Tanaka, M. Tamura, Y.Nishio, K. Kajita and T. Mori: "Discontinuous Change of MetalInaulator Transition in the Alloyed q-system : θ-(BEDT-TTF)_2(Rb_<1-x>, Cs_x)Zn(SCN)_4"J. Phys. Soc. Jpn. 69. 1751 (2000)

H. Mori、T. Okano、S. Tanaka、M. Tamura、Y.Nishio、K. Kajita 和 T. Mori：“合金 q 系统中 MetalInaulator 转变的不连续变化：θ-(BEDT-TTF)_2( Rb_<1-x>, Cs_x)Zn(SCN)_4"J. Phys. Soc. Jpn. 69. 1751 (2000)