Novel phases of electronic Mott insulators

Massachusetts Institute Of Technology, Cambridge MA

Investigators

Abstract

Technical summary This award supports theoretical research and education to study novel Mott insulating states of electronic matter. Specific phases of interest are quantum spin liquids, and phases of quantum magnetism that are the spin analogs of interacting topological insulators. The emphasis will be on the development of theoretical concepts and methods which will be placed in the context of experiments and/or numerical work. The PI will pursue three topics: (i) the theory and phenomenology of quantum spin liquids in the organic salts and other materials; (ii) a theoretical description of a new class of gapless quantum spin liquid states that are likely beyond the existing paradigm; (iii) the theory and realization of spin analogs of topological insulators. Projects (i) and (ii) are motivated by experiments on many Mott insulators that provide evidence for various kinds of quantum spin liquid phases, typically with gapless excitations. Project (iii) is on a new and rapidly evolving area which can deepen our understanding both of quantum magnetism and topological insulators. The award supports the training of graduate students in modern concepts and methods in condensed matter physics. Undergraduates will be involved in the research. The PI will develop lectures to expose graduate students to the phenomenology of correlated materials and their experimental probes. He will also develop lectures to convey the excitement of condensed matter physics to other scientists. Non-technical summary This award supports theoretical research and education on interesting new kinds of insulating states of matter. It has long been known that in certain materials insulating behavior develops as a result of the Coulomb interaction between the electrons rather than due to the filling of quantum mechanical energy bands. Modern developments show that some of these Mott insulators can be in very novel states of matter where the microscopic degrees of freedom are quantum mechanically entangled over macroscopic distances. Several unusual counter intuitive phenomena arise as a result of the long range quantum mechanical entanglement. The PI will develop new concepts and methods to deal with insulators with long range quantum entanglement, and their experimental signatures. He will also develop a deeper understanding of the interplay between symmetry and quantum effects in such interaction driven insulators. This fundamental research has potential to generate concepts that will underlie future quantum technologies. The study of long range entangled phases is a relatively new chapter in condensed matter physics which holds promise to have similar impact on technology as the previous chapter of the study of long range ordered phases. This award also supports the training of graduate students in modern concepts and methods in condensed matter physics. Undergraduates will be involved in the research. The PI will develop lectures to expose graduate students to the phenomenology of correlated materials and their experimental probes. He will also develop lectures to convey the excitement of condensed matter physics to other scientists.