Тип публикации: статья из журнала
Год издания: 1996
Аннотация: In the context of the problem of the ground state in the U = ? Hubbard model, the normal (nonmagnetic) state of the system (N state) is considered over the whole range of possible electron concentrations n. The energy of normal state ?(1) 0 (n) calculated in the generalized Hartree-Fock approximation is smaller than the energy of sПоказать полностьюaturated ferromagnetic state ?FM(n). A nominally exact representation for the self-energy operator of the single-particle Green's function is obtained. It may be approximated by an expression Mk(E) ? ?F(E), where ? is the parameter of kinematic correlation interaction and F(E) is the exact single-site Green's function. For the elliptic density of states, the integral equation in F(E) has been solved exactly. It is shown that the spectral intensity satisfies the exact sum rule and the energy of the strongly correlated N state satisfies the inequality ?0(n) ?FM(n). The distribution function of electrons strongly deviates from the Fermian steplike shape at T = 0: it changes gradually in the whole range of allowed energies, so that the jump at the value of chemical potential is absent. A suggestion is made that in the thermodynamic limit, the ground state of the system is singlet.
Журнал: Physics of Metals and Metallography
Выпуск журнала: Vol. 81, Is. 5
Номера страниц: 480-490