Fermi Surface Reconstruction in Cuprate High Temperature Superconductors

超导体有可能彻底改变世界用电的方式。这些材料已经有许多实际应用，从能源运输到医疗诊断、通信和大众运输。然而，为了产生更广泛的影响，我们需要发现比今天已知的性能更好的材料。为了调整这些性质并指导新材料的研究，非常需要了解这些材料超导的基本物理原因。虽然这是已知的所谓的传统材料，大多数发现于1980年之前，超导机制负责氧化铜高温超导，发现于1986年，仍然缺乏理解。该提案中的研究旨在推进我们对氧化铜高温超导体电子结构的理解。我们相信，这些知识将提供一个重要的一步，在世界范围内寻求了解，从而改善这些材料。我们提出了一个广泛的计划，将研究这些材料的非常有序的样品的热力学和量子相干特性。在有序度较低的样品中，基本的破环相变的特征可能会被模糊，使它们在实验中不可见。此外，量子相干效应提供了关于电子结构的独特信息，但由于无序而无法观察到。我们将使用过去20年开发的技术来生长高度有序的单晶样品，并研究它们在世界上最高的可用磁场下的行为，该磁场高达100 T（大约是地球磁场的200万倍），温度低于绝对零度以上1度。从这些测量中，我们将发现费米面如何随着电子浓度的变化而变化，费米面表征了材料中载流电子的动量分布。这将提供独特的和重要的信息，以指导在这些材料的超导理论的发展。

Superconductors have the potential to revolutionise the way the world uses electricity. There are already many practical applications of these materials, ranging from energy transport to uses in medical diagnosis, communications and mass people transport. However for more wide-ranging impact we need to discover materials which have even better properties than are already known today. In order to tune these properties and to guide the search for new materials, knowledge of the fundamental physical reasons why these materials are superconducting is highly desirable. Although this is known for so-called conventional materials, mostly discovered before 1980, an understanding of the superconducting mechanism responsible for copper oxide based high temperature superconductivity, discovered in 1986, is still lacking. The research in this proposal aims to advance our understanding of the electronic structure of copper oxide high-temperature superconductors. We believe this knowledge will provide a major step forward in the world-wide quest to understand and hence improve these materials.We are proposing a wide ranging programme which will study the thermodynamic and quantum coherent properties of extremely well ordered samples of these materials. In less well ordered samples, the signatures of the fundamental symmetry-breaking phase transitions may be smeared out, making them invisible to experiment. Also quantum coherence effects which give unique information about the electronic structure are made unobservable by disorder. We will use techniques developed over the last twenty years to grow highly ordered single crystal samples and study their behaviour under the world's highest available magnetic fields of up to 100 T (which is roughly 2 million times larger than the earth's field) at temperatures less than one degree above absolute zero. From these measurements we will discover how the Fermi surface, which characterises the momentum distribution of the current carrying electrons in the material, evolves with electron concentration. This will give unique and important information to guide the development of a theory of superconductivity in these materials.