Strongly Correlated Quantum Materials

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Much of today’s industry relies on advanced materials whose development from discovery to commercial product takes decades. The United States is funding the “Materials Genome Initiative” to “speed up our understanding of the fundamentals of material science providing a wealth of practical information that entrepreneurs and innovators will be able to use to develop new products and processes”. In particular, “The initiative funds computational tools, software, new methods for material characterization, and the development of open standards and databases.” This type of fundamental research is as important for Canada as it is for the United States and the world. The students that will participate in the development of fundamental knowledge will be especially skilled to recognize the opportunities brought about by this knowledge and to understand the advantages and limitations of the tools necessary to apply the fundamental research. We will contribute to this effort by focusing on computational tools for materials whose spectacular properties are consequences of the non-trivial quantum mechanical nature of matter. Quantum mechanics allows electrons to be at the same time localized as particles, or propagating as waves. It also allows interacting electrons in a piece of matter to behave in a highly organized, collective way. Materials with these properties are called strongly correlated quantum materials. Examples of spectacular collective electronic properties include high-temperature superconductivity and perfect metallic behavior at the surfaces of topological insulators. High-temperature superconductors carry electricity without resistance at temperatures half-way between absolute zero and room temperature. A room temperature superconductor would lead to a revolution in technology, from power lines to transport and electronics. There are two broad classes of objectives for this five-year research program. First, we will continue to develop computational tools for high-temperature superconductors from a very general perspective. These materials are strongly correlated. More specifically, strongly correlated superconductivity pushes theoretical methods in the most difficult regime, namely in the vicinity of the interaction-induced metal-insulator transition, where the localized and wave picture of electrons are equally important. Strongly correlated superconductivity is strongest for the critical interaction strength of this transition, whether it is induced by adding/removing conduction electrons, as in ceramics based on copper-oxygen planes (cuprates), or by pressure, as in layered organic compounds. By keeping this general point of view, were cuprates and layered organics are considered within the same framework, we believe we can firmly establish that these methods give us the main ingredients for a theory of strongly correlated superconductivity that has predictive power. The other broad class of objectives is to develop the computational tools for strongly correlated quantum materials. For example, we will include software developed for models in computer codes that aim at making realistic predictions of materials from first principles. And we will also develop new methods that will allow us to include physical effects that could not be taken into account before in first-principle codes, increasing significantly the reliability of predictions.