Global entanglement in XXZ chains

N. CANOSA; R. ROSSIGNOLI

PHYSICAL REVIEW A - ATOMIC, MOLECULAR AND OPTICAL PHYSICS

APS

Lugar: New York; Año: 2005

1050-2947

      We examine the thermal entanglement of XXZ type Heisenberg chains in the  presence of  a  uniform  magnetic  field  along  the  z  axes,  through the evaluation  of  the  negativity associated  with  bipartite  partitions of  the  whole  system  and  subsystems. Limit temperatures for non-zero global negativities are shown to depend  on the asymmetry  Delta  but  not  on  the  uniform  field,  and  can  be  much  higher   than those limiting pairwise entanglement.  It  is  also  shown that global bipartite   entanglement may exist for  T>0  even for  Delta geq 1,  i.e.,  when the system is   fully aligned (and hence separable) at T=0, and  that the bipartition leading  to the highest  limit temperature depends  on Delta.