Quantum Phase Transitions and Heat Capacity in a two-atoms Bose-Hubbard   Model
  We show that a two-atoms Bose-Hubbard model exhibits three different phases in the behavior of thermal entanglement in its parameter space. These phases are demonstrated to be traceable back to the existence of quantum phase transitions in the same system. Significant similarities between the behaviors of thermal entanglement and heat capacity in the parameter space are brought to light thus allowing to interpret the occurrence and the meaning of all these three phases. 
B. Leggio, A. Napoli, A. Messina
quant-ph cond-mat.quant-gas