Structural basis for understanding phase transitions in 3-dimensional charge-density-wave compounds

理解 3 维电荷密度波化合物相变的结构基础

• 批准号: 265092781
• 负责人: Professor Dr. Sander van Smaalen
• 金额: --
• 依托单位: Laboratorium für Kristallographie
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2014
• 资助国家: 德国
• 起止时间: 2013-12-31 至 2018-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/265092781?language=en
• 关键词: Structural; basis; understanding; phase; transitions

Phase transitions towards charge-density wave (CDW) states are often associated with the low-dimensional character of the electron bands in metallic materials. The CDW phase diagram is not understood for substances without obvious low-dimensional features of their crystal structures and physical properties. The proposed project is concerned with the study of CDW phase transitions in the 3-dimensional CDW compounds Lu2Ir3Si5, NiV2S4 (Cr3S4 structure type) and CuV2S4 (Spinel structure type) by means of temperature-dependent single-crystal X-ray diffraction. An important result of these experiments will be the periodic lattice distortion (PLD) associated with the CDW. The PLD provides conclusive information about the location of the CDW within the unit cell of the crystal structure, about the importance of frustrated interactions, about the symmetry (1-q or 2-q state) of the CDW, and about the phonons that may participate in the stabilisation of the CDW state. Diffraction experiments will also be used for analysing further phase transitions (for example a possible occurrence of a lock-in transition) and for the determination of the temperature dependence of the order parameter. The experimental information will be used for theoretical considerations towards understanding the mechanism of the phase transitions and explaining the nature of the physical properties within the CDW state.

金属材料中向电荷密度波(CDW)态的相变通常与电子能带的低维特性有关。对于没有晶体结构和物理性质的明显低维特征的物质，CDW相图是不能理解的。本项目是用变温单晶X射线衍射法研究三维CDW化合物Lu2Ir3Si5、NiV2S4(Cr3S4结构型)和CuV2S4(尖晶石型)的CDW相变。这些实验的一个重要结果将是与CDW相关的周期性晶格失真(PLD)。PLD提供了有关CDW在晶体结构的晶胞内的位置、受挫相互作用的重要性、CDW的对称性(1-Q或2-Q态)以及可能参与CDW态稳定的声子的确凿信息。衍射实验还将用于分析进一步的相变(例如，可能发生的锁定相变)，并用于确定序参数的温度依赖性。这些实验信息将被用于理解相变机制和解释CDW态中物理性质的理论考虑。