The entanglement of Heisenberg chain with next-nearest-neighbor   interaction
  The features of the concurrences of the nearest-neighbor and the next-nearest-neighbor sites for one-dimensional Heisenberg model with the next-nearest-neighbor interaction are studied both at the ground state and finite temperatures respectively. Both concurrences are found to exhibit different behaviors at the ground state, which is clarified from the point of view of the correlation function. The threshold temperature with respective to different number of sites and the thermal concurrences of the system up to 12 sites are studied numerically. 
Shi-Jian Gu, Haibin Li, You-Quan Li, and Hai-Qing Lin