Interactions and Coherence in Lanthanide Metallic Compounds

摘要：本项目研究了一种新的由镱、铟和铜组成的金属间化合物，该化合物具有复杂的物理性质，对其的理解将对凝聚态物理领域产生重大影响。该化合物具有一阶相变，晶格常数和价电子不连续变化，但对称性不变。此外，在以银取代铟获得的一系列化合物中遇到了新的热力学性质。主要研究人员已经成功地完成了这些材料的单晶生长的艰巨任务，这些材料将通过电阻率、磁化率、热膨胀、弹性常数和中子散射作为温度、压力和磁场的函数来详尽地表征。根据这些高度相关的电子或“重费米子”材料的电子和磁性，将努力理解相变的基础，从而确定状态方程。摘要：少数金属表现出类似于气体凝结成液体的性质：当温度低于临界温度时，密度不连续地变化，而晶体对称性没有变化。金属的磁性强度也随之下降。这个项目的研究人员最近学会了如何生长一种新的金属间化合物的大晶体，显示出缩合行为。该项目包括对该化合物及其合金的结构、磁性和电子行为进行彻底的研究。目标是了解驱动凝结的电子之间相互作用的本质，特别是材料的磁性和它的内聚能之间似乎存在微妙的相互作用。这样的研究将提高我们对固体中电子在晶体状态下帮助原子进行相干键合的条件的理解。研究结果可为整个金属物理和磁学领域提供重要信息。

9501529 Fisk Technical Abstract: This project investigates a new intermetallic compound of ytterbium, indium, and copper, with physical properties which display a complex character and whose understanding would have major impact on the field of condensed matter physics. The compound has a first-order phase transition where the lattice constant and valence change discontinuously with no change in symmetry. Additional, novel thermodynamic properties are encountered in the series of compounds obtained by substitution of silver for indium. The principal investigators have succeeded in the difficult task of growing single crystals of these materials which will exhaustively characterized via resistivity, susceptibility, thermal expansion, elastic constants and neutron scattering as a function of temperature, pressure and magnetic field. The equation of state will be determined in an effort to understand the basis for the phase transition in terms of electronic and magnetic properties of these highly correlated electron, or "heavy fermion", materials. %%% Non-Technical Abstract: A small number of metals exhibit a property analogous to the condensation of a gas to a liquid: as the temperature is lowered below a critical temperature, the density changes discontinuously, with no change in crystal symmetry. There is an accompanying decrease in the strength of the magnetism of the metal. The investigators in this project have recently learned how to grow large crystals of a new intermetallic compound displaying the condensation behavior. The project involves a thorough investigation of the structure, magnetism, and electronic behavior of the compound and its alloys. The goal is to understand the nature of the interactions between electrons which drive the condensation, in particular there seems to be subtle interplay between the magnetism of the material and its cohesi ve energy. Such studies will improve our understanding of the conditions under which electrons in solids help to coherently bond the atoms in the crystalline state. The results may provide important information for the entire field of metal physics and magnetism.