Field tuned atom-atom entanglement via diople-dipole interaction
  We propose a simple scheme, in which only one atom couples to a cavity field, to entangle two two-level atoms. We connect two atoms with dipole-dipole interaction since one of them can move around the cavity. The results show that the peak entanglment does not depend on dipole-dipole interaction strength but on field density at a certain controlling time. So the field density can act as a switch for maximum entanglement (ME) generation. 
Yan-Qing Guo, Hai-Jing Cao, and He-Shan Song