Extended quantum U(1)-liquid phase in a three-dimensional quantum dimer   model
  Recently, quantum dimer models, in which the system can tunnel between different classical dimer configurations, have attracted a great deal of interest as a paradigm for the study of exotic quantum phases. Much of this excitement has centred on the claim that a certain class of quantum dimer model, defined on a bipartite lattice, can support a quantum U(1)-liquid phase with deconfined fractional excitations in three dimensions. These fractional monomer excitations are quantum analogues of the magnetic monopoles found in spin ice. In this article we use extensive quantum Monte Carlo simulations to establish the ground-state phase diagram of the quantum dimer model on the three-dimensional, bipartite, diamond lattice as a function of the ratio {\mu} of the potential to kinetic energy terms in the Hamiltonian. We find that, for {\mu}_c = 0.75 +/- 0.04, the model undergoes a first-order quantum phase transition from an ordered "R-state" into an extended quantum U(1)-liquid phase, which terminates in a quantum critical "RK point" for {\mu}=1. This confirms the published field-theoretical scenario. We present detailed evidence for the existence of the U(1)-liquid phase, and indirect evidence for the existence of its photon and monopole excitations. We also explore some of the technical ramifications of this analysis, benchmarking quantum Monte Carlo against a variety of exact and perturbative results, comparing different variational wave functions. The ergodicity of the quantum dimer model on a diamond lattice is discussed in detail. These results complete and extend the analysis previously published in [O. Sikora et al., Phys. Rev. Lett. 103, 247001 (2009)]. 
Olga Sikora, Nic Shannon, Frank Pollmann, Karlo Penc and Peter Fulde
cond-mat.str-el cond-mat.stat-mech