Oxford Quantum Condensed Matter Theory Grant

凝聚态物理学是研究我们周围物质世界的科学。当人们在最小尺度上考察材料时--它们的原子和电子--不可避免地要用到量子力学。研究物质的性质如何依赖于量子物理学是量子凝聚态理论的范围，也是本研究计划的主题。在过去的一百年里，许多最重要的技术进步都归功于量子凝聚态理论的根本性突破：晶体管的发明导致了现代计算机工业的发展，这取决于对固体中电子量子理论的理解;激光的发展，导致了现代光通信网络，依赖于对固体中光的量子特性的理解;磁共振成像是现代医学的一个重要工具，它是在对量子水平上的磁性进行了多年研究之后才出现的。也许这个领域以及所有凝聚态物理学的中心问题是，如何描述具有许多组成部分的物理系统-例如固体中的许多电子-它们都相互作用。虽然这种由许多部分组成的系统是不可能复杂的--描述所有部分的运动是完全没有希望的--但上个世纪的物理学告诉我们，复杂的背后往往是简单和结构。这只是一个找到正确描述的问题。令人惊讶的是，由许多相互作用的部分产生的简单结构可能与底层成分的结构截然不同。这种所谓的涌现现象，是凝聚态理论的主要焦点。一个戏剧性的例子是分数量子霍尔物理学，其中完全由电子组成的流体，量子力学合谋产生粒子，只有一个电子的三分之一的电荷。涌现现象的影响是深远的，并对上个世纪的大部分时间里一直在物理学中占据主导地位的还原论哲学的普遍存在提出了质疑-认为理解的最佳途径是分开研究。牛津大学的量子凝聚态理论小组对该领域中一些最重要的悬而未决的问题应用了广泛的理论方法。虽然各个项目可能在细节上有所不同，但它们通过在复杂的量子多粒子系统中寻找涌现结构和简单性而紧密相连。它们还通过几个共同的子主题进一步统一起来：（一）非平衡量子多体系统的研究，即，许多粒子的量子力学系统，其中基于热力学的众所周知和众所周知的理论结构无法应用。(ii)在纳米尺度系统中研究电子的集体行为，其中强相互作用的多粒子物理学在近分子尺度上遇到量子世界。(iii)非常规秩序的研究，这是涌现的结构，如分数量子霍尔效应，其中新的结构（或秩序）出现，这是非常不同的组成部分。我们坚信，在这些令人兴奋的理论方向上的持续研究将为未来的技术开辟新的可能性-就像上个世纪理论凝聚态物理学毫无疑问所做的那样。

Condensed matter physics is the science of the material world around us. When one examines materials on the smallest scales - their atoms and electrons - inevitably, quantum mechanics comes into play. The study of how properties of matter depend on quantum physics is the purview of quantum condensed matter theory, and the topic of this research programme. Over the last hundred years, many of the most important advances in technology owe their existence to fundamental breakthroughs in quantum condensed matter theory: The invention of the transistor, which resulted in the modern computer industry, depended on an understanding of the quantum theory of electrons in solids; the development of the laser, which resulted in modern optical communication networks, relied on the understanding of quantum properties of light in solids; magnetic resonance imaging, a key tool of modern medicine, came only after many years of study of the properties of magnetism on the quantum level. Perhaps the central question in this field, and in all of condensed matter physics, is how to describe physical systems with many constituent pieces -such as many electrons in a solid - which are all interacting with each other. While such systems with many pieces are impossibly complex - it is entirely hopeless to describe the motions of all of the pieces - the last century of physics has taught us that simplicity and structure is frequently behind the complex. It is 'just' a matter of finding the right description. Surprisingly, the simple structure which arises from the many interacting pieces can be radically different from the structure of the underlying constituents. Such so-called emergent phenomena , are a major focus of condensed matter theory in general. A dramatic example of this is given by fractional quantum Hall physics, where a fluid made up entirely of electrons, quantum mechanically conspires to produce particles with only a third of the charge of a single electron. The implications of emergent phenomena are far reaching, and raise questions about the ubiquity of the reductionist philosophy that has implicitly dominated much of physics for most of the last century - the view that the best route to understanding is to divide and study pieces individually. The Oxford quantum condensed matter theory group applies a wide range of theoretical approaches to some of the most important outstanding questions in the field. While the individual projects may differ in detail, they are deeply connected by the search for emergent structure and simplicity in otherwise complex quantum many-particle systems. They are further united by several common sub-themes: (i) The study of non-equilibrium quantum many-body systems, i.e., quantum mechanical systems of many particles where the well-known and well-understood theoretical structures based on thermodynamics fail to apply. (ii) The study of collective behaviour of electrons in nanoscale systems, where strongly interacting many-particle physics meets the quantum world on the near-molecular scale.(iii) The study of unconventional orders, which are emergent structures, like the fractional quantum hall effect, where new structure (or order ) arises that is very different from that of the constituent pieces. We firmly believe that continued study in these exciting theoretical directions will lead to the opening of new possibilities for the technologies of the future - in the same way that the last century of theoretical condensed matter physics has unquestionably done.