PAIRWISE ENTANGLEMENT IN THE TETRAHEDRAL LATTICE WITH HEISENBERG INTERACTIONS

摘要

By using the concept of negativity, we determine entanglement features of the tetrahedral lattice with Heisenberg interactions. It is found that except N-1,N-1 for the case of (1/2-1/2-1-1) mixed spins, there is no pairwise entanglement between any two spins at any temperature when B=0. When B increases after B=0, the ground-state negativities exhibit square wave or stepwise structures, and experience sharply descents to lower values at some energy-level crossing points. For thermal entanglement, the negativities exhibit ridge-like or staircase structures as B increases, and there are regions in the B-T plane where an increase of temperature may help to enhance the entanglement.