Studies of quasicrystals and their approximants

凝聚态物理学的进步往往需要发现和发展新材料，以扩展或挑战目前的理解。这项建议既涉及新材料的合成，也涉及对其物理性质的研究。该提案涉及当前感兴趣的一类特定材料，即准晶。准晶是1984年发现的一种新的固体形式，它不同于其他两种形式的晶体和非晶态，它具有一种新的长程有序，称为准周期性，以及与经典禁止的五重、八重、十重和十二重对称轴相关的非晶体取向有序。凝聚态物理的核心问题之一是确定准周期性是否会产生与晶体和非晶态材料显著不同的新的物理性质。这项提议将试图通过实验回答准晶物理学的四个突出问题来发现这种新的性质。准晶中实现了哪些类型的长程准周期磁序？电子态密度的预测精细结构在准晶中实现了吗？极大的电阻率及其非金属温度依赖于准晶的本征性质吗？理论能够预测具有特定物理性质的新准晶吗？这项提议将通过合成几类新的准晶和相应的晶体近似物，并用一系列现代实验技术研究它们的磁性、电子结构和电子输运性质来解决这四个突出问题。这一提议的最终结果将是对这些新材料的基本物理性质有更清晰和更完整的了解，这可能会导致找到准晶的工业应用。此外，十几名高素质的人员将获得一系列与合成和测量相关的实用技能，这些技能将帮助他们在加拿大工业的高科技部门或学术界找到工作。

Advances in condensed matter physics often require the discovery and development of new materials that extend or challenge the current understanding. This proposal addresses both the synthesis of new materials and the investigation of their physical properties. The proposal is concerned with one specific class of materials that are of current interest, namely quasicrystals. Discovered in 1984, quasicrystals are a new form of solid that differs from the two other forms, crystalline and amorphous, by possessing a new type of long-range order, called quasiperiodicity, and noncrystallographic orientational order associated with classically forbidden fivefold, eightfold, tenfold, and twelvefold symmetry axes. One of the central problems in condensed matter physics is determining whether quasiperiodicity leads to novel physical properties which are significantly different from those of crystalline and amorphous materials. This proposal will attempt to discover such novel properties by experimentally answering four outstanding questions of the physics of quasicrystals. What types of long-range quasiperiodic magnetic order are realized in quasicrystals? Is the predicted fine structure of the electronic density of states realized in quasicrystals? Are the extremely large values of the electrical resistivity and its nonmetallic temperature dependence the intrinsic properties of quasicrystals? Is theory capable of predicting new quasicrystals with specific physical properties? This proposal will address these four outstanding questions via the synthesis of several families of new quasicrystals and corresponding crystalline approximants and the investigation of their magnetic, electronic structure, and electronic transport properties with an array of modern experimental techniques. The end product of this proposal will be a much clearer and more complete understanding of the basic physical properties of these new materials, that may possibly lead to finding industrial applications of quasicrystals. In addition, a dozen highly qualified personnel will acquire a range of practical synthesis and measurement related skills that will help them to find employment in the high-technology sector of Canadian industry or in academia.