Density-matrix functional theory of the attractive Hubbard model: Statistical analogy of pairing correlations

Figure: Average number of double occupation D, kinetic energy T and Bloch state occupation numbers η of the 2D negative U Hubbard model as a function of the interaction strength U < 0. Results obtained from lattice density-functional theory and the independent fermion entropy ansatz are compared with exact diagonalizations.

Reference: T. S. Müller and G. M. Pastor, arXiv:2110.07422 [cond-mat.str-el], submitted to Physical Review B