Growth, Characterization and Electronic Structure Studies of the Non-Fermi Liquid Compound YbAlB4

对限制在原子晶格中的电子的研究为固体量子理论奠定了理论基础，在固体量子理论中，电子被视为波而不是粒子。在20世纪的大部分时间里，这一理论被成功地用于制造我们在日常生活中变得如此熟悉的电子产品所用的材料。例如，计算机、iPod和移动电话中的电路是由连接半导体晶体管的小金属线组成的，半导体晶体管是只有使用量子理论才能完全理解其功能的元件。这一理论成功的关键是假设材料中的电子行为或多或少是独立的；我们可以将它们相互之间的影响视为独立电子情况下的弱扰动。这一粗略的近似确实有效，这一事实相当引人注目，因为一块金属的立方厘米内的电子数量与整个宇宙中的恒星数量一样多。尽管这张简单的图片取得了显著的成功，但越来越多的材料被发现，在这些材料中，几乎独立的电子的假设似乎被打破了。物理学家现在面临的挑战是如何超越这种近似值？当晶格中的电子被强迫发生强烈相互作用时，固体的量子理论会发生什么？这在材料中产生了什么新的物质状态，这种材料表现出了什么新的性质？这些问题的答案不仅有望扩展我们的基础物理知识，而且还提供了开发和设计未来设备的机会，使用由强电子相互作用产生的显示出新特性的材料。其中独立电子图像分解的材料的一个例子是新合成的化合物YbAlB4。有证据表明，这种材料在低温下即将具有磁性，这种接近磁性的方式导致了不寻常的行为。一个例子是，YbAlB4传输电流的能力不会以传统金属理论可以理解的方式随温度变化。要理解是什么导致了这种奇怪的行为，一个有用的方法是测量材料中的电子在外加磁场存在时的行为。行进电子的路径被一个场所偏转，对于足够强的场，它可以弯曲到足以形成一个闭合的圆。在非常低的温度下研究这种效应使我们能够测量电子之间的相互作用，这为我们深入了解为什么YbAlB4等材料的行为与正常金属如此不同。

The study of electrons confined within a crystal lattice of atoms yielded the theoretical foundation for the quantum theory of solids, where electrons are treated as waves instead of particles. Through much of the 20th century this theory was utilized with great success to engineer the materials used in creating the electronics we have become so familiar with in our everyday lives. The circuits found in computers, iPods and mobile phones are for instance constructed from small metal wires connecting semiconductor transistors -- elements whose function can only be fully understood using quantum theory. The key to the success of this theory is the assumption that electrons within a material behave more or less independently; we can think of their effects on each other as merely a weak perturbation on the independent electron case. The fact that this crude approximation works at all is rather remarkable, there are as many electrons confined within a single cubic centimeter of a metal as there are stars in the entire universe.Despite the remarkable success of this simple picture, an increasingly large number of materials have been discovered in which the assumption of nearly independent electrons appears to break down. The challenge now facing physicists is how does one move beyond this approximation? What happens to the quantum theory of solids when electrons in a crystal lattice are forced to interact strongly? What new states of matter does this produce in materials, and what new properties do such materials exhibit? The answers to these questions promises not only to expand our knowledge of fundamental physics, but also offer the opportunity to develop and engineer devices of the future, using materials exhibiting novel properties arising from strong electron interactions. One example of a material in which the independent electron picture breaks down is the newly synthesized compound YbAlB4. Evidence suggests that this material is on the verge of being magnetic at low temperatures, and this close proximity to magnetism leads to unusual behaviour. One example is that the ability of YbAlB4 to transport electrical current does not vary with temperature in a way that can be understood using conventional theories of metals.A useful approach to understanding what leads to such strange behaviour is to measure how the electrons in a material behave in the presence of an applied magnetic field. The path of a travelling electron is deflected by a field, and for sufficiently strong fields may bend enough to form a closed circle. Studying this effect at very low temperatures allows us to measure interactions between electrons, which offers insight into why materials such as YbAlB4 behave so differently from normal metals.