Excitations, Topological Defects and Quantum Transport in Superconductors and Superfluid 3He in Confined Geometries

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TECHNICAL SUMMARYThis award supports research and education in theoretical condensed matter physics for the prediction and discovery of physical properties, particularly non-equilibrium phenomena, in quantum liquids, random solids, superconductors, and heterogeneous electronic and magnetic materials. This research responds in part to recent discoveries and predictions of new phases of condensed matter, including "topological condensed matter", in which the both topology and symmetry play central roles in determining their physical properties. Specific studies that will be pursued with this award include the development of quantitative signatures based on mass, spin and charge transport, acoustic and optical spectroscopy of topological excitations in superconductors and quantum fluids. Closely related research includes theoretical investigations of collective surface excitations and non-equilibrium properties of superfluid helium-three and chiral spin-triplet superconductors, e.g. Sr2RuO4 and UPt3, in thin films, conducting channels, and point contacts. A key goal is to predict and quantify signatures of surface states and their transport properties for topological superconductors and superfluids. Another thread in this research is the investigation of vortices and domain walls, and mechanisms of dissipation in topological superconductors and superfluids. This topic is important for understanding limits of the concept of "topological protection" in condensed matter. Finally, the PI will employ theoretical models and statistical methods for analyzing the interplay between ordering associated with symmetry breaking phase transitions, transport in quantum fluids and solids and extrinsic disorder that is present in virtually all macroscopic forms of matter. The proposed theoretical developments connect with experimental studies of the quantum liquid phases of helium-three infused into ultra-low density silica glass, called aerogel. These studies are important to our basic understanding of condensed matter, and hold promise for transformational applications. Quantum condensed phases, topological condensed matter, novel electronic superconductors and heterogeneous superconducting and magnetic materials have potential for next-generation electronic devices for quantum information and computation.The research has a strong education component involving the training of graduate students and a continuation of the PI's history and commitment in recruiting undergraduates in cutting edge research projects. The research involves substantial international collaboration with research teams in the United Kingdom, France and Japan focused on the proposed research, which will enrich the research enterprise in the physical sciences in the US.NON-TECHNICAL SUMMARYThis award supports research and education in theoretical condensed matter physics for the prediction and discovery of physical properties, particularly those that are realized in situations far from equilibrium, in superfluids and superconductors, and in various electronic and magnetic materials that can support so-called "topological phases". Superfluidity is a state of matter in which the matter behaves like a fluid without any viscosity and maintains the same temperature throughout itself. At low temperatures, superconductors have the property that electricity can flow through them without any resistance. Topological phases, new states of matter with exotic properties, exhibit a very subtle type of internal organization of electrons, and are believed to hold the key to building a new generation of fault-tolerant computers that employ quantum mechanics to drastically outperform today's fastest computers for certain tasks. The properties of such materials are governed by the laws of quantum physics and organizing mathematical principles based on symmetry and topology, which is a major area of mathematics that deals with spatial properties preserved under continuous deformations of objects. The research relates to recent experimental discoveries establishing the existence of new quantum phases of liquid helium confined in small regions of space, such as cavities that are some 100 times smaller than the human hair, droplets or ultra-thin channels and films, superconducting materials whose electrical properties co-exist with magnetic properties, and hybrid materials composed of superconductors, magnets and the so-called "topological insulators" that cannot conduct electricity in their interior but allow movement of charges on their edges or boundaries. The research focuses on confined geometries because new physical properties are predicted to occur on surfaces and interfaces of these materials. Many properties of condensed matter that have been predicted and discovered as a result of basic research have resulted in applications and new technologies, from instrumentation for medial diagnostics to electronic and magnetic devices for information storage and high-speed computation that have transformed our society. Topological condensed matter in confined geometries, new electronic materials and heterogeneous superconducting and magnetic materials have potential for next-generation electronic devices for quantum information and computation.The research program has a strong education component involving the training of graduate students and a continuation of the PI's history and commitment in recruiting undergraduates in cutting edge research projects. The research involves substantial international collaboration with research teams in the United Kingdom, France and Japan focused on the proposed research, which will enrich the research enterprise in the physical sciences in the US.