Search for: All records

Quantum spin liquids are exotic phases of quantum matter especially pertinent to many modern condensed matter systems. Dirac spin liquids (DSLs) are a class of gapless quantum spin liquids that do not have a quasi-particle description and are potentially realized in a wide variety of spin 1 / 2 magnetic systems on 2 d lattices. In particular, the DSL in square lattice spin- 1 / 2 magnets is described at low energies by ( 2 + 1 ) d quantum electrodynamics with N f = 4 flavors of massless Dirac fermions minimally coupled to an emergent U ( 1 ) gauge field. The existence of a relevant, symmetry-allowed monopole perturbation renders the DSL on the square lattice intrinsically unstable. We argue that the DSL describes a stable continuous phase transition within the familiar Neel phase (or within the Valence Bond Solid (VBS) phase). In other words, the DSL is an "unnecessary" quantum critical point within a single phase of matter. Our result offers a novel view of the square lattice DSL in that the critical spin liquid can exist within either the Neel or VBS state itself, and does not require leaving these conventional states. 

We propose PartGAN, a novel generative model that disentangles and generates background, object shape, object texture, and decomposes objects into parts without any mask or part annotations. To achieve object-level disentanglement, we build upon prior work and maximize the mutual information between the generated factors and sampled latent prior codes. To achieve part-level decomposition, we learn a part generator, which decomposes an object into parts that are spatially localized, disjoint, and consistent across instances. Extensive experiments on multiple datasets demonstrate that PartGAN discovers consistent object parts, which enable part-based controllable image generation.