Extended quantum dimer model and novel valence-bond phases

Abstract

We extend the quantum dimer model (QDM) introduced by Rokhsar and Kivelson so as toconstruct a concrete example of the model which exhibits the first-order phase transitionbetween different valence-bond solids suggested recently by Batista and Trugman and lookfor the possibility of other exotic dimer states. We show that our model contains threeexotic valence-bond phases (herringbone, checkerboard and dimer smectic) in theground-state phase diagram and that it realizes the phase transition from thestaggered valence-bond solid to the herringbone. The checkerboard phase hasfour-fold rotational symmetry, while the dimer smectic, in the absence of quantumfluctuations, has massive degeneracy originating from partial ordering only inone of the two spatial directions. A resonance process involving three dimersresolves this massive degeneracy and the dimer smectic becomes ordered (order fromdisorder).