title: Exact spin liquid ground states of the quantum dimer model on the square and honeycomb lattices.
abstract: We study a generalized quantum hard-core dimer model on the square and honeycomb lattices, allowing for first and second neighbor dimers. At generalized Rokhsar-Kivelson points, the exact ground states can be constructed, and ground-state correlation functions can be equated to those of interacting (1+1)-dimensional Grassmann fields. When the concentration of second neighbor dimers is small, the ground-state correlations are shown to be short ranged corresponding to a (gaped) spin liquid phase. On a 2-torus, the ground states exhibit fourfold topological degeneracy. On a finite cylinder we have found a dramatic even-odd effect depending on the circumference and propose that this can be used as a numerical diagnostic of gapped spin-liquid phases, more generally.
authors.affiliation: Department of Physics, Stanford University, Stanford, California 94305, USA.
authors.forename: Hong
authors.initials: H
authors.lastname: Yao
authors.forename: Steven A
authors.initials: SA
authors.lastname: Kivelson