Michael Hermele

Projected-wave-function study of the spin-1/2 Heisenberg model on the Kagomé lattice.

We perform a Gutzwiller projected-wave-function study for the spin-1/2 Heisenberg model on the Kagomé lattice to compare energies of several spin-liquid states. The result indicates that a U(1)-Dirac spin-liquid state has the lowest energy. Furthermore, even without variational parameters, the energy turns out to be very close to that found by exact diagonalization. We show that such a U(1)-Dirac state represents a quantum phase whose low-energy physics is governed by four flavors of two-component Dirac fermions coupled to a U(1) gauge field. These results are discussed in the context of recent experiments on ZnCu(3)(OH)(6)Cl(2).

Mott Insulators of Ultracold Fermionic Alkaline Earth Atoms: Underconstrained Magnetism and Chiral Spin Liquid

We study Mott insulators of fermionic alkaline earth atoms, described by Heisenberg spin models with enhanced SU(N) symmetry. In dramatic contrast to SU(2) magnetism, more than two spins are required to form a singlet. On the square lattice, the classical ground state is highly degenerate and magnetic order is thus unlikely. In a large-N limit, we find a chiral spin liquid ground state with topological order and Abelian fractional statistics. We discuss its experimental detection. Chiral spin liquids with non-Abelian anyons may also be realizable with alkaline earth atoms.

Atomic Quantum Simulator for Lattice Gauge Theories and Ring Exchange Models

We present the design of a ring exchange interaction in cold atomic gases subjected to an optical lattice using well-understood tools for manipulating and controlling such gases. The strength of this interaction can be tuned independently and describes the correlated hopping of two bosons. We discuss a setup where this coupling term may allow for the realization and observation of exotic quantum phases, including a deconfined insulator described by the Coulomb phase of a three-dimensional U(1) lattice gauge theory.

Classifying fractionalization: symmetry classification of gapped Z2 spin liquids in two dimensions

We classify distinct types of quantum number fractionalization occurring in two-dimensional topologically ordered phases, focusing in particular on phases with

Probing the Kondo lattice model with alkaline-earth-metal atoms

{\mathbb{Z}}_{2}

Fracton topological order via coupled layers

topological order, that is, on gapped

Hallmarks of the Mott-metal crossover in the hole-doped pseudospin-1/2 Mott insulator Sr2IrO4

{\mathbb{Z}}_{2}

Magnetic orders and topological phases fromf-dexchange in pyrochlore iridates

spin liquids. We find that the fractionalization class of each anyon is an equivalence class of projective representations of the symmetry group, corresponding to elements of the cohomology group

Monopoles in CP{sup N-1} model via the state-operator correspondence

{H}^{2}(G,{\mathbb{Z}}_{2})

Quantum spin ices and topological phases from dipolar-octupolar doublets on the pyrochlore lattice.

. This result leads us to a symmetry classification of gapped