Critical dynamics in frustrated systems and spin liquids

凝聚态物理学的主要目标之一是发现具有新颖且潜在有用性质的新材料。但是，由于这必须使用与“普通”物质相同的基本成分--质子、中子、电子--来实现，所以新奇之处必须来自它们的组合方式，以及各部分相互作用以产生不同整体的方式。即使它们的组成部分很简单，具有许多强相互作用部分的系统也很难从理论上理解。因此，凝聚态物理学的进展依赖于新的理论策略的发展，以理解复杂系统中大尺度行为的出现。寻找具有新特性的材料的一个有希望的地方是“受抑磁体”，即被阻止或至少被阻碍形成我们所熟悉的通常磁状态的系统。在物理学中，挫折是指存在竞争的相互作用，不能同时得到满足，并发生在某些材料包含局部磁矩，或“自旋”。在受抑磁体中出现的一种特别新颖的物质形式是所谓的自旋液体，其中磁矩是强烈相关的，但不会形成有序的结构，类似于普通液体（如水）中分子的密集但无序的排列。例子包括“自旋冰”材料，它具有许多不寻常的磁性，包括托管粒子，表现为磁单极子。目前，人们正在进行大量的实验和理论工作，以了解这些材料的性质，并预测和发现它们可能表现出的新现象。本研究项目将开发一种新的理论方法，以探索受抑系统的动力学，包括受抑磁体，如自旋冰。该战略将是利用系统在相变附近的特殊性质，即随着温度（或另一物理参数）的变化而发生的突然和戏剧性的行为差异，例如从液态水到蒸汽的转变。通过开发和应用新的理论和计算技术，这项基础研究将为受挫折材料的未来技术应用铺平道路。

One of the major goals of condensed matter physics is to discover new materials with novel, and potentially useful, properties. But since this must be achieved using the same basic constituents - protons, neutrons, electrons - as "ordinary" matter, the novelty must come from how they are combined, and the ways in which the parts interact with each other to give a different whole. Even when their constituents are simple, systems with many strongly interacting parts are difficult to understand theoretically. Progress in condensed matter physics therefore relies on the development of new theoretical strategies for understanding the emergence of large-scale behaviour in complex systems.A promising place to look for materials with novel properties is in "frustrated magnets", systems that are prevented, or at least hindered, from forming the usual magnetic states with which we are familiar. In physics, frustration refers to the presence of competing interactions that cannot simultaneously be satisfied, and occurs in certain materials containing localised magnetic moments, or "spins". A particularly novel form of matter that occurs in frustrated magnets is the so-called spin liquid, where the magnetic moments are strongly correlated but do not settle into an ordered configuration, analogous to the dense but disordered arrangement of molecules in an ordinary liquid such as water. Examples include the "spin ice" materials, which have a number of unusual magnetic properties, including hosting particles that behave as magnetic monopoles. Much experimental and theoretical work is currently under way to understand the properties of these materials, as well as to predict and discover new phenomena that they may exhibit.This research project will develop a new theoretical approach to explore the dynamics of frustrated systems, including frustrated magnets such as spin ice. The strategy will be to exploit the peculiar properties of systems near phase transitions, sudden and dramatic differences in behaviour that occur as temperature (or another physical parameter) changes, such as the transition from liquid water to steam. By developing and applying new theoretical and computational techniques, this fundamental research will pave the way for future technological applications of frustrated materials.