Abstract
2+1d U(1) Chern-Simons (CS) gauge theories provide a simple and complete description of all 2+1d Abelian topological phases. In this talk, we discuss how the theoretical framework can be used to explore new possibilities in the world of 3+1d quantum phases of matter. The 3+1d generalization involves an infinite number of 2+1d U(1) gauge fields, which can be thought of as living in different layers, coupled through CS terms. When the theory is fully gapped, it describes a kind of fracton topological order, where all particles are restricted to move in planes. We will discuss how these new examples compare with existing constructions of fracton order. Perhaps even more interestingly, for certain couplings the theory can become gapless. We will discuss our current understanding of the nature of the gapless theories, with the help of a microscopic realization in terms of coupled wire constructions. We will argue that these models realize new types of compressible quantum liquids.
Biography
Prof. Meng Cheng is an Assistant Professor of Physics at Yale University. He received his undergraduate degree from Nanjing University. In 2013, he obtained his Ph.D. degree from the University of Maryland, College Park, where he studied topological superconductivity and its applications in quantum information processing. He then moved to a postdoctoral researcher position in Microsoft Research, Station Q in Santa Barbara, during which he investigated the interplay of global symmetry and topological quantum order. He joined the Department of Physics at Yale University in 2016.