Von Neumann and Renyi Entanglement Entropies in Spin Ladders

Density matrix renormalization group (DMRG) algorithm has proven a useful tool to calculate entanglement properties of one- and quasi-one-dimensional condensed matter systems, due to the fact that the reduced density matrix eigenvalue spectrum for some bipartitions of the system is avaliable as a by-product of the algorithm. In this talk, I will present calculations of the von Neumann and Renyi entanglement entropies (EE) on Heisenberg ladders up to seven legs using DMRG. For a bipartition into subregions A and B, the EE for even-leg ladders is constant for subregion sizes larger than the correlation length, while for odd-leg ladders has a logarithmic dependence on the subregion size. Our results indicate that in the limit of a large number of legs the von Neumann EE obeys an area law.