Entanglement in dimerized spin s chains

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

Paraty

Workshop; VI Quantum Information School and Workshop - Paraty 2017; 2017

INCT-IQ CAPES - Altos Estudos CNPq FAPESP

We examine the entanglement in the ground state (GS) of finite dimerized spin-s chains interacting through anisotropic XY couplings immersed in a transverse magnetic field, by means of exact results and a self-consistent generalized mean field approximation (GMF) based on independent pairs. The approach %, which makes no a priori assumptions on the pair states, predicts, for sufficiently low coupling between pairs, 2s distinct dimerized phases for increasing fields below the pair factorizing field, separated by spin parity breaking phases (PBP). The dimerized phases lead to approximate magnetization and pair entanglement plateaus, while thePBP exhibit weak pair entanglement but non-negligible entanglement of the pair with the rest of the system. These predictions are confirmed by exact results for finite $s = 1$ and $s = 3/2$ chains. The large $s$ limit of the dimerized pair entanglement is also analyzed, showing saturation in the $XY$ case but remaining unbounded in the $XX$ case.