Ground state properties of the simplified hubbard model

This paper presents the exact solution of the simplified Hubbard model in which only one kind of electrons can hop and this quantum mechanical hopping of electrons is assumed to be unconstrained. It is shown that the model still behaves non-trivially, although it no longer depends on the lattice structure and the dimensionality of the system. For this case the authors find: a gap in the ground state energy always exists at the half-filled band point (n = 1), a preferred magnetic state at n = 1 and large U is a total spin singlet, U-dependence of the ground state energy has qualitatively the same form as one of the conventional Hubbard model with the (t2/U)-behavior at large U. A phase diagram of the model is discussed