Аннотация: The problem of the ground state of the electronic system in the Hubbard model for U=infinity is discussed. The author investigates the normal (singlet or nonmagnetic) N state of the electronic system over the entire range of electron densities n less than or equal to 1. It is shown that the energy of the N state epsilon(0)((1))(n) in a one-particle approximation, such as (e.g.) the extended Hartree-Fock approximation, is lower than the energy of the saturated ferromagnetic FM state epsilon(FM)(n) for all n. The dynamic magnetic susceptibility is calculated in the random phase approximation, and it is shown that the N state is stable over the entire range of electron densities: The static susceptibility (omega=0) does not have a band singularity in the zero-wave vector limit q--0. A formally exact representation is obtained for the mass operator of the one-particle Green's function, and an approximation of this operator is proposed: M-k(E)similar or equal to lambda F(E), where lambda=n(1-n)/(1-n/2)z is the kinematic interaction parameter, z is the number of nearest neighbors, and F(E) is the total single-site Green's function. For an elliptical density of states the integral equation for F(E) is solved exactly, ad it is shown that the spectral intensity rigorously satisfies the sum rule. The calculated energy of the strongly correlated N state epsilon(0)(n)epsilon(FM)(n) for all n, and in light of this relationship the author discusses the hypothesis that the ground state of the system is the normal (singlet) state in the thermodynamic limit. The electron distribution function at T
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Держатели документа:
L.V. Kirenskii Inst. of Phys., Siberian Br. Russ. Acad. of Sci., 660036 Krasnoyarsk, Russian Federation
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Доп.точки доступа:
Кузьмин, Евгений Всеволодович