Modified Two-Pole Approximation
for Systems with Strong Electron
Correlations: Peculiarities of Spectrum
and DOS
L. Didukh, O. Kramar, Yu. Dovhopyaty, and Yu. Skorenkyy
In a new variant of Hartree–Fock approximation for the calculation of electrical
and magnetic properties of strongly correlated electron systems in nanoscale material, the quasiparticle energy spectrum is obtained. The spectrum is temperatureand concentration-dependent, exact in atomic and band limits and gives a consistent description of the metal–insulator transition at temperature change or under the
external pressure application. Refinement of the initial approach has allowed us to
take into account the energy states widening which caused an essential transformation
of the electron density of energy states. The single-particle Green function is calculated analytically, and model DOS features are discussed in detail for various values
of energy parameters of the model and applied for investigation of low-temperature
antiferromagnetic phase and possible phase transitions under the external influences.
The electron–hole asymmetry in the model reflects a peculiar behavior of specific
nanomaterials, generalizing the Hubbard model and t–J model. Hopping integrals
are renormalized by electron correlations and appear to be concentration-dependent.
As a consequence, at change of conductance type, the bandwidth, activation energy,
and conductivity are found to undergo sharp changes.
1 Introduction
For nanoscale systems’ theoretical description, the improvement of both analytic and
numerical methods of treatment for strong electron correlations in a wide range of
electron concentration and energy parameters is instrumental.
L. Didukh · O. Kramar (B) · Yu. Dovhopyaty · Yu. Skorenkyy
Ternopil Ivan Puluj National Technical University, 56, Rus’ka St., 46001 Ternopil, Ukraine
e-mail: okramar18@gmail.com
© Springer Nature Switzerland AG 2021
O. Fesenko and L. Yatsenko (eds.), Nanomaterials and Nanocomposites,
Nanostructure Surfaces, and Their Applications, Springer Proceedings
in Physics 246, https://doi.org/10.1007/978-3-030-51905-6_10
129
for Systems with Strong Electron
Correlations: Peculiarities of Spectrum
and DOS
L. Didukh, O. Kramar, Yu. Dovhopyaty, and Yu. Skorenkyy
In a new variant of Hartree–Fock approximation for the calculation of electrical
and magnetic properties of strongly correlated electron systems in nanoscale material, the quasiparticle energy spectrum is obtained. The spectrum is temperatureand concentration-dependent, exact in atomic and band limits and gives a consistent description of the metal–insulator transition at temperature change or under the
external pressure application. Refinement of the initial approach has allowed us to
take into account the energy states widening which caused an essential transformation
of the electron density of energy states. The single-particle Green function is calculated analytically, and model DOS features are discussed in detail for various values
of energy parameters of the model and applied for investigation of low-temperature
antiferromagnetic phase and possible phase transitions under the external influences.
The electron–hole asymmetry in the model reflects a peculiar behavior of specific
nanomaterials, generalizing the Hubbard model and t–J model. Hopping integrals
are renormalized by electron correlations and appear to be concentration-dependent.
As a consequence, at change of conductance type, the bandwidth, activation energy,
and conductivity are found to undergo sharp changes.
1 Introduction
For nanoscale systems’ theoretical description, the improvement of both analytic and
numerical methods of treatment for strong electron correlations in a wide range of
electron concentration and energy parameters is instrumental.
L. Didukh · O. Kramar (B) · Yu. Dovhopyaty · Yu. Skorenkyy
Ternopil Ivan Puluj National Technical University, 56, Rus’ka St., 46001 Ternopil, Ukraine
e-mail: okramar18@gmail.com
© Springer Nature Switzerland AG 2021
O. Fesenko and L. Yatsenko (eds.), Nanomaterials and Nanocomposites,
Nanostructure Surfaces, and Their Applications, Springer Proceedings
in Physics 246, https://doi.org/10.1007/978-3-030-51905-6_10
129