Approaching the absolute zero of temperature via absorbing energy

For the Blume–Emery–Griffiths (BEG) model with a positive biquadratic coupling and without the ferromagnetic coupling, the microcanonical ensemble predicts that the entropy of this model is a multivalued and non-concave function of the energy, leading to an absolute zero temperature at its highest energy level. Via increasing the energy of a BEG system, its temperature can get close to absolute zero in local microcanonical dynamics . By building up a weak coupling between two identical BEG subsystems with their energies equal to half of the highest value of the energy of this model, one subsystem can absorb energy from another and both of them evolve to the absolute zero of temperature. Graphic abstract