| We investigate both analytically and numerically the entanglement hamiltonian of various one dimensional quantum spin chains like the XXZ and the J1 J2 spin chain. By means of exact diagonalization techniques we obtain the full entanglement spectrum of these models. Such quantity is an extension of the entanglement entropy and it is known to contains much more complete information about the system. By perturbation theory calculations we characterize the main features of the entanglement spectrum of these models making predictions that we checked with the exact diagonalization results. We compare our results with the free fermions case (XX spin chain) where the entanglement hamiltonian is known analytically. |
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