Prof. Nic Shannon iUniversity of Bristol and University of Tokyoj
"First numerical evidence for a U(1) liquid phase in a 3D quantum dimer model"

Recently, it has been suggested that in the quantum dimer model on a bipartite lattice in 3D, a U(1) liquid extends for a finite range of parameters bordering the quantum-critical ``Rokhsar-Kivelson'' (RK) point [1,2]. Such a quantum liquid phase would have extremely interesting properties, including a new form of effective electromagnetism, and deconfined fractional excitations. Here we present the results of an extensive numerical study of the quantum dimer model on a diamond lattice, using variational and Green's function Monte Carlo simulation techniques. Our results confirm explicitly the existence of the three phases conjectured for this model --- a 16-sublattice ordered ``R state'' with cubic symmetry, a set of isolated states and, separating them, a U(1) liquid phase terminating at the RK point. Notably, in the liquid phase, we are able to reproduce the finite size energy spectra predicted by the corresponding U(1) gauge theory.
[1] R. Moessner and S.L. Sondhi, Phys. Rev. B 68, 184512 (2003).
[2] D.L. Bergman, G.A. Fiete, and L. Balents, Phys. Rev. B 73, 134402 (2006).