Nonequilibrium States of Topological Quantum Fluids and Unconventional Superconductors

Northwestern University, Evanston IL

Investigators

Abstract

NON-TECHNICAL SUMMARY The research made possible with this award is directed toward prediction and discovery of the thermal, electrical and magnetic properties of a new class of materials described as "topological" materials. The properties of these materials are governed by the laws of quantum physics and organizing principles based on the mathematics of symmetry and topology, the latter of which can be visualized as the properties of matter that are insensitive to deformations. The research focuses on the prediction of the properties of topological phases of matter, particularly topological superconductors, superfluids, and hybrid systems composed of insulators and superconductors, which are driven out of equilibrium by electric and magnetic fields or by contact with other materials. The emphasis will be on systems that are 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, because unique physical properties are predicted to occur on surfaces and interfaces of topological 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 medical diagnostics to electronic and magnetic devices for information storage and high-speed computation. These discoveries have led to technologies that have transformed our society. There is reasoned expectation that discoveries in topological condensed matter will lead to next-generation electronic and magnetic devices, with potential societal impacts that range from significant to transformative. This research project also has strong education components involving the training of graduate students as next generation of research leaders, and a continuation of the PI's commitment in recruiting undergraduates into cutting edge research projects. The proposed research involves international collaborations with researchers in the United Kingdom and Japan which will enrich the research enterprise in physical sciences in the US. TECHNICAL SUMMARY This award supports research and education in theoretical physics of newly discovered and newly predicted quantum phases of matter, particularly topological superfluids, liquid helium-three, and unconventional superconductors, including candidates for topological superconductivity, strontium ruthenate, uranium platinum-three, copper bismuth selenide, and heavy electron materials exhibiting coexistent ferromagnetism and superconductivity. The proposed research is focused on investigations of topological condensed matter out of equilibrium, with the goal of predicting and interpreting experimental observations on, and signatures of, topological quantum phases of matter under non-equilibrium conditions. A key goal of this research is a quantitative and predictive theory of the non-equilibrium response and dynamics of topological superconductors and superfluids. Specific studies that will be pursued with this award include the development of quantum transport equations for the distribution functions for edge and surface states, the dynamical equations for the non-equilibrium spectral functions for these states, the development of microscopic models for surface and interface boundary conditions, and the effects of back-action of the bulk, including possible coupling to Bosonic collective modes. A second thread in this research is the investigation of the dynamics of vortices, domain walls and impurities, and mechanisms of dissipation in topological superconductors and superfluids. A third line of research employs theoretical models and statistical methods for analyzing the interplay between topological order and extrinsic disorder that is present in virtually all macroscopic forms of matter. There is reasoned expectation that discoveries in topological condensed matter, including matter in confined geometries, new electronic materials and heterogeneous superconducting and magnetic materials, will lead to next-generation quantum electronic and magnetic devices, with potential societal impacts that range from significant to transformative. This research project also has strong education components involving the training of graduate students as next generation of research leaders, and a continuation of the PI's commitment in recruiting undergraduates into cutting edge research projects. The proposed research involves international collaborations with researchers in the United Kingdom and Japan which will enrich the research enterprise in physical sciences in the US.