Frustrated Antiferromagnets with Entanglement Renormalization: Ground State of the Spin-1/2 Heisenberg Model on a Kagome Lattice

Entanglement renormalization techniques are applied to numerically investigate the ground state of the spin- 1/2 Heisenberg model on a kagome lattice. Lattices of N = {36, 144, infinity} sites with periodic boundary conditions are considered. For the infinite lattice, the best approximation to the ground state is found to be a valence bond crystal with a 36-site unit cell, compatible with a previous proposal. Its energy per site, E = -0.432 21, is an exact upper bound and is lower than the energy of any previous (gapped or algebraic) spin liquid candidate for the ground state.