Unconventional phase transitions and correlated dynamics in frustrated systems

点击翻译按钮获取中文摘要

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 that the parts interact with each other, to give a different whole. Even when their constituents are simple, complex 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, as well as new computational techniques to simulate them.It has recently been appreciated that a promising place to look for materials with novel properties is in so-called "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 localized magnetic moments, or spins.Examples of particular recent interest are the "spin ices", a family of compounds containing either dysprosium or holmium. These elements are highly magnetic, and are used for example in computer hard drives. The particular atomic arrangement in the spin ice compounds frustrates this magnetic tendency, leading to disordered systems where the individual moments fluctuate rather than forming an ordered structure. Among their many interesting properties, the spin ices are believed to host particles that behave as magnetic monopoles, long conjectured to exist as fundamental particles, but never observed. Both experimental and theoretical work is needed to understand the properties of these materials, to predict and discover new phenomena that they may host, and to extend this to other related systems.This project will explore the properties of frustrated systems, including frustrated magnets such as spin ice, by developing new theoretical and computational techniques. In particular, they will be studied through 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. Phase transitions can occur in frustrated magnets in the presence, for example, of externally applied magnetic fields, and can provide a unifying perspective on a number of frustrated systems.