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

金属络盐(DME-DCNQI)_2Cu在微压下表现出重入金属-绝缘体的转变。位于费米能级附近的DCNQIπ电子和Cu3d电子的混合产生了3dFermi面，抑制了低维不稳定性。我们进行了甲基的氢化反应，它的大小可以控制电子尺寸和调节重入的M-I相变。我们实验研究了DCNQI-Cu体系的重入金属-绝缘体-金属相变的机理。用热弛豫法(0.5&lt；T&lt；40K)、绝热脉冲法(20&lt；T&lt；100K)和差热分析法(DTA)测量了不同化学压力下样品的比热和潜热。根据实验结果，我们确定了金属相和绝缘相之间的吉布斯自由能差，并成功地绘制了能很好地再现实验结果的相图。我们得出结论，自由电子(金属相)到具有1/2自旋的局域电子(绝缘相)的自由能变化是驱动该系统反常相变的关键。此外，我们还阐明了晶格系统的贡献。在这个氢化体系中，我们发现了(DME-DCNQI)_2Cu体系的两种反常比热，其中一个氢化甲基的取向自由给体系带来了两种反常比热。在含一个氢原子的甲基体系(CH_2D)中，我们发现了肖特基比热。在含有CHD_2的体系中，我们观察到非肖特基类型的峰。为了找出这些反常现象的来源和机制，我们对CH2D和CHD_2组成的混晶进行了热研究，阐明了CHD_2分子在DCNQI-Cu体系中沿c轴的构象有序性。

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.