We study the effects of correlated hopping in the two-dimensional (2D) Falicov-Kimball model by means of an extension of the dynamical mean-field approximation (DMFA). The extension is based on the projection technique and the DMFA, in which nonlocal correlations are taken into account through static quantities of a relevant subspace. The effect of the correlated hopping is to introduce nonlocal self-energy components which remain even at D → ∞. We show that the sum rules of the spectral function and its moments are preserved. The spectral function obtained reveals significant nonlocal contributions which are absent in the DMFA.

Thanh-Hai D., Minh-Tien T.

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Từ khóa : Electron energy levels; Fermions; Green's function; Hamiltonians; Phase transitions; Spectrum analysis; Correlated hopping; Strongly correlated electron systems (SCES); Superconducting materials