Entanglement spectra of quantum Heisenberg ladders
Résumé
Bipartite entanglement measures have become very useful tools to investigate quantum phases of correlated electrons. Here, I analyze the entanglement spectrum of gapped two-leg quantum Heisenberg ladders on a periodic ribbon partitioned into two identical periodic chains. Comparison of various entanglement entropies proposed in the literature is given. The entanglement spectrum is shown to exhibit low-energy towers of states reminiscent of the gapless spectrum of each individual chain. A mapping of the reduced density matrix to a thermodynamic density matrix is proposed via the introduction of an effective temperature, enabling to identify the ladder spin correlation length with a thermal length.