Modified Two-Pole Approximation for Systems with Strong Electron Correlations …
137
Fig. 2 DOS for the generalized Hubbard model with correlated hopping of electrons in approximation I at U/w = 2.1 (the upper panel) and the proposed approximation at U/w = 1.8 (the lower
panel), semi-elliptic bare DOS. Black (the lowest) line is for τ 1 = τ 2 = 0; blue line is for τ 1 = τ 2 =
0.05 (the upper panel), for τ 1 = τ 2 = 0.1 (the lower panel); red line corresponds to τ 1 = τ 2 = 0.2
3 Results and Discussion
Let us consider the energy spectrum (29) at condition (U + ε 2 − ε 1 )
2
>> (4dt(k))
which corresponds to the state of Mott–Hubbard insulator or semimetal. Then
E 1
k
= −μ + ε 1 + (1 − 2d)t
k
,
(31)
137
Fig. 2 DOS for the generalized Hubbard model with correlated hopping of electrons in approximation I at U/w = 2.1 (the upper panel) and the proposed approximation at U/w = 1.8 (the lower
panel), semi-elliptic bare DOS. Black (the lowest) line is for τ 1 = τ 2 = 0; blue line is for τ 1 = τ 2 =
0.05 (the upper panel), for τ 1 = τ 2 = 0.1 (the lower panel); red line corresponds to τ 1 = τ 2 = 0.2
3 Results and Discussion
Let us consider the energy spectrum (29) at condition (U + ε 2 − ε 1 )
2
>> (4dt(k))
which corresponds to the state of Mott–Hubbard insulator or semimetal. Then
E 1
k
= −μ + ε 1 + (1 − 2d)t
k
,
(31)