Julia Wildeboer

Spin glassiness and power law scaling in anisotropic triangular spin-1/2 antiferromagnets

We present data on the magnetic properties of two classes of layered spin S=1/2 antiferromagnetic quasi-triangular lattice materials: Cu2(1?x)Zn2x(OH)3NO3(0?x?0.65) and its long-organic-chain?intercalated derivatives Cu2(1?x)Zn2x(OH)3(C7H15COO)?mH2O(0?x?0.29), where non-magnetic Zn substitutes for Cu isostructurally. It is found that the intercalated compounds, even in a clean system in the absence of dilution, x=0, show spin glass behaviour, as evidenced by DC and AC susceptibility, and by time-dependent magnetization measurements. A striking feature is the observation of a sharp crossover between two successive power law regimes in the DC susceptibility above the freezing temperature. In constrast to standard theoretical expectations, these power laws are insensitive to doping. Specific heat data are consistent with a conventional phase transition in the unintercalated compounds, and glassy behaviour in the intercalated compounds.

Entanglement Entropy and Topological Order in Resonating Valence-Bond Quantum Spin Liquids

On the triangular and kagome lattices, short-ranged resonating valence bond (RVB) wave functions can be sampled without the sign problem using a recently-developed Pfaffian Monte Carlo scheme. In this paper, we study the Renyi entanglement entropy in these wave functions using a replica-trick method. Using various spatial bipartitions, including the Levin-Wen construction, our finite-size scaled Renyi entropy gives a topological contribution consistent with

Spin correlations and topological entanglement entropy in a non-Abelian spin-one spin liquid

\gamma = \text{ln}(2)

Destruction of valence-bond order in a S=1/2 sawtooth chain with a Dzyaloshinskii-Moriya term

, as expected for a gapped

Ground state uniqueness of the twelve site RVB spin-liquid parent Hamiltonian on the kagome lattice

\mathbb{Z}_{2}

Correlation functions in SU(2)-invariant resonating-valence-bond spin liquids on nonbipartite lattices.

quantum spin liquid. We prove that the mutual statistics are consistent with the toric code anyon model and rule out any other quasiparticle statistics such as the double semion model.

Emergent symmetry at a transition between intertwined orders in a

We analyze the properties of a non-Abelian spin-1 chiral spin liquid state proposed by Greiter and Thomale [PRL 102, 207203 (2009)] using variational Monte Carlo. In this state the bosonic

S=1

\nu = 1

magnet

Moore-Read Pfaffian wave function is used to describe a gas of bosonic spin flips on a square lattice with one flux quantum per plaquette. For toroidal geometries there is a three-dimensional space of these states corresponding to the topological degeneracy of the bosonic Moore-Read state on the torus. We show that spin correlations for different states in this space become indistinguishable for large system size. We also calculate the Renyi entanglement entropy for different system partitions to extract the topological entanglement entropy and provide evidence that the topological order of the lattice spin-liquid state is the same as that of the continuum Moore-Read state from which it is constructed.

Quasielectrons in lattice Moore-Read models.

A small value of the spin gap in quantum antiferromagnets with strong frustration makes them susceptible to nominally small deviations from the ideal Heisenberg model. One such perturbation, the anisotropic Dzyaloshinskii-Moriya (DM) interaction, is an important perturbation for the S = 1/2 kagome antiferromagnet, one of the current candidates for a quantum-disordered ground state. We study the influence of the DM term in a related one-dimensional system, the sawtooth chain, which has valence-bond order in its ground state. Through a combination of analytical and numerical methods, we show that a relatively weak DM coupling, 0.115J, is sufficient to destroy the valence-bond order, close the spin gap, and turn the system into a Luttinger liquid with algebraic spin correlations. A similar mechanism may be at work in the kagome antiferromagnet.