Global entanglement in XXZ chains

N. CANOSA; R. ROSSIGNOLI

PHYSICAL REVIEW A - ATOMIC, MOLECULAR AND OPTICAL PHYSICS

APS

Lugar: New York; Año: 2006 vol. 73 p. 223471 - 223478

1050-2947

We examine the thermal entanglement of  XXZ - type Heisenberg chains in thepresence of a uniform magnetic field along the  z  axes, through the evaluationof the negativity associated with bipartitions of the whole system andsubsystems. Limit temperatures for non-zero global negativities are shown todepend on the asymmetry  D  but not on the uniform field, and can be muchhigher than those limiting  pairwise entanglement. It is also shown that globalbipartite entanglement may exist for T>0 even for  D > 1, i.e., whenthe system is fully aligned (and hence separable) at T=0, and that thebipartition leading to the highest limit temperature depends on D .