Quantum Phenomena in Solids

University Of California-Santa Barbara, Santa Barbara CA

Investigators

Abstract

NONTECHNICAL SUMMARY This award supports fundamental research and education on understanding and controlling quantum properties of materials. Fundamentally, everything on Earth is governed by quantum mechanics. Yet, while quantum theory is essential to understanding the gross properties of materials, for example the existence of both metals and insulators and the phenomena of magnetism, it rarely manifests itself directly in the more macroscopic world. This project aims to bridge this gap by investigating materials in which quantum effects are unusually apparent in laboratory-scale observations. These quantum materials offer new functionalities that could not be achieved in more classical substances. The project has three main thrusts. The first targets materials that are topological and magnetic. Topological materials have a kind of internal "twist" that leads to novel conducting properties. By combining this with magnetism, control over those properties may be achieved. The second thrust focuses on emergent "quasiparticles"--objects that behave like fundamental particles of nature but modified in essential ways--with the unusual property that they are confined to fewer than the usual 3 dimensions. The third problem addressed is how to modify the properties of materials using powerful laser light. The forces from such powerful light can reorganize the electrons in a material, giving them new and interesting properties. This research involves a combination of development of theoretical techniques, numerical and analytical calculations, and close interplay with experimental studies. Graduate and undergraduate students will be involved in an essential way in the research, and will be trained broadly in analytical reasoning, mathematical methods, computation, and scientific communication, which form the basis for many careers in STEM fields, both in and out of physics. TECHNICAL SUMMARY The award supports fundamental research and education towards understanding and controlling quantum correlations in solids. In the long term, there are two goals to the program: to develop new materials and structures with useful functionality not currently available, and to extend the basic scientific framework to understand matter in new regimes and new phases. There are three main topics: 1) Interplay of real space and momentum space topology in itinerant magnets; 2) Sub-dimensional dynamics; 3) Driven dynamics of Mott insulators. The research will be carried out using a diverse set of theoretical techniques: phenomenological modeling, statistical mechanics, field theory, ab initio simulations, many-body numerics such as Monte Carlo methods and variational wavefunctions, and symmetry analysis. In general, the intellectual merit of the research is in developing and bringing deep theoretical ideas in the theory of quantum matter to fruition in real materials. The first topic on momentum and real space topology is a next step after the maturation of the field of topological band theory, and opens the door to a rich interplay of phenomena bringing together topological aspects of electronic structure and frustrated magnetism. The second subject is both related to the frontier of topological phases and qualitatively new forms of three-dimensional matter, and also is a point where powerful theoretical techniques from one dimension can be brought to bear on difficult problems of dynamics. The final area of driven dynamics is a nascent field, in which a rapid growth of new theoretical ideas surrounding Floquet many-body problems, combined with experimental advances in ultrafast technology, offers opportunities for new physics in the solid state. Graduate and undergraduate students will be involved in an essential way in the research, and will be trained broadly in analytical reasoning, mathematical methods, computation, and scientific communication, which form the basis for many careers in STEM fields, both in and out of physics. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.