Density-matrix renormalization-group study of entanglement and entropy in an antiferromagnetic Heisenberg spin chain with domain walls

Abstract

By using the method of density-matrix renormalization-group theory, the ground-state entanglement in the spin-1/2 isotropic antiferromagnetic Heisenberg chain is studied when there are domain walls generated by a boundary magnetic field. It is found that the pairwise entanglement of odd-bond two qubits decreases and even-bond two qubits increases to stable values alternately when the magnetic field increases. The pairwise entanglement of odd bond can be equal to that of even bond for a suitable value of the magnetic field. When the magnetic field increases further, the entanglement of even bond can be larger than that of odd bond. The entanglement entropy increases and then almost saturates as the number of spin sites increases. Due to the domain walls, the entanglement entropy of even bond decreases to a minimum value and then increases as the magnetic field increases.