Thermal entanglement of Hubbard dimers in the nonextensive statistics

The thermal entanglement of the Hubbard dimer (two-site Hubbard model) has been studied with the nonextensive statistics. We have calculated the auto-correlation (Oq), pair correlation (Lq), concurrence (Γq) and conditional entropy (Rq) as functions of entropic index q and the temperature T. The thermal entanglement is shown to considerably depend on the entropic index. For q<1.0, the threshold temperature where Γq vanishes or Rq changes its sign is more increased and the entanglement may survive at higher temperatures than for q=1.0. Relations among Lq, Γq and Rq are investigated. The physical meaning of the entropic index q is discussed with the microcanonical and superstatistical approaches. The nonextensive statistics is applied also to Heisenberg dimers.