New Emergent Quantum States of Matter at High Pressure

At ambient conditions, the light alkali metals Li, Na and K are nearly free electron (NFE) metals. But rather than becoming MORE free-electron like when compressed, these metals undergo transitions to unusual and complex structural and electronic forms as a result of density-driven changes in the interactions of the ions and electrons. While such behaviour is expected in all high-density matter, the physics is most evident in the alkali metals due to their NFE behaviour at ambient conditions, and their very high compressibilities. They thus offer a unique insight into the behaviour of all other metals at very high densities. We will exploit our team's expertise in experimental high-pressure physics to create solid and fluid alkali metals at unprecedented densities, and then determine their structural behaviour using x-ray diffraction techniques at synchrotrons, x-ray free electron lasers, and high-energy laser facilities. We will then use electronic structure and quantum-molecular-dynamics calculations to understand the physics behind the observed behaviour, and thereby develop new understanding and improved predictive capabilities in the behaviour of matter at ultra-high densities.

Knowledge Impact: Developing a detailed knowledge of how simple metals and their melts actually behave at very high compression, and then developing the computational tools to model and understand that behaviour, will generate impact both in the immediate scientific areas of condensed matter physics and high energy-density physics, and also in other areas where high-density matter is prevalent, such as planetary science and inertial confinement fusion (ICF). The new knowledge provided by our research will enable the behaviour of high-density matter to be computed more accurately at conditions even more extreme than we plan to attain here. Economic and societal impacts will derive from the knowledge outcomes of the project, and from the computational methods which will be developed and implemented in standard software packages.

By deepening our understanding of the physical properties of matter at high pressure, we will provide standardized computational tools for calculating electronic and structural properties at high pressures. These tools will help other researchers to understand why high-density materials behave as they do, and make it possible to identify materials with specific desirable properties and even to design new materials.

People and Training: The scale of this project provides an excellent opportunity to train the next generation of researchers in a variety of state-of-the-art x-ray and laser experimental techniques, as well as computation and theoretical modelling. This importance of this training aspect has been recognised by our Project Collaborator AWE who have funded two CASE studentships for the project. Each student and postdoc involved in the research will benefit from the diverse range of experimental and computational techniques we will employ, making them highly employable at new facilities such as ESRF-EBS and European-XFEL, and also at government laboratories, including AWE.

Outreach: The project will impact on society through outreach activities aimed at explaining the exciting magnetic and electronic phenomena found in materials which have correlated electrons and dense electrons. Members of the public, high school students and prospective university students will be able to attend our Science Festivals and Open Days or participate in workshops aimed at de-mystifying the fundamental science in the project.