Pair entanglement in dimerized spin-s chains

A. BOETTE; R. ROSSIGNOLI; N. CANOSA; J.M. MATERA

PHYSICAL REVIEW B - CONDENSED MATTER AND MATERIALS PHYSICS

APS

Lugar: New York; Año: 2016 vol. 94 p. 2144031 - 21440311

0163-1829

We examine the pair entanglement in the ground state of finite dimerized spin-s chains interacting through anisotropic XY couplings immersed in a transverse magnetic field by means of a self-consistent pair mean-field approximation. The approach,which makes noapriori assumptions on the pair states, predicts, for sufficiently low coupling between pairs, 2s distinct dimerized phases for increasing fields belowthe pair factorizing field, separated by spin-parity-breaking phases. The dimerized phases lead to approximate magnetization and pair entanglement plateaus, while the parity-breaking phases are characterized by weak pair entanglement but non-negligible entanglement of the pair with the rest of the system. These predictions are confirmed by the exact results obtained in finite s = 1 and s = 3/2 chains. It is also shown that for increasing values of the spin s, the entanglement of an isolated pair, as measured by the negativity, rapidly saturates in the anisotropic XY case but increases as s 1/2 in the XX case, reflecting a distinct single-spin entanglement spectrum.