Quantum Dimer Model — Resonating Valence Bond State

Quantum dimer model: dimers cover the lattice (hard-core constraint). Hamiltonian H = −t·Σ(|⟲⟩⟨⟳| + h.c.) + v·Σn_p. At t=v (Rokhsar-Kivelson point), ground state is the equal-weight superposition of all dimer coverings = RVB liquid. v≫t: staggered order. t≫v: plaquette or columnar order. The RVB liquid has Z₂ topological order (fractionalized spinons).