The resistance and thermoelectric coefficient in layered structures with anisotropic energy spectrum
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PALISTRANT, Maria, URSU, Vitalie. The resistance and thermoelectric coefficient in layered structures with anisotropic energy spectrum. In: Materials Science and Condensed Matter Physics, Ed. 6, 11-14 septembrie 2012, Chișinău. Chișinău, Republica Moldova: Institutul de Fizică Aplicată, 2012, Editia 6, p. 44. ISBN 978-9975-66-290-1.
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Materials Science and Condensed Matter Physics
Editia 6, 2012
Conferința "Materials Science and Condensed Matter Physics"
6, Chișinău, Moldova, 11-14 septembrie 2012

The resistance and thermoelectric coefficient in layered structures with anisotropic energy spectrum


Pag. 44-44

Palistrant Maria, Ursu Vitalie
 
Institute of Applied Physics
 
Disponibil în IBN: 5 martie 2020


Rezumat

In the last few years, scientists have focused on the intensive research of high-temperature compounds on the basis of the FeAs ( iron - oxypnictides ). A great interest in these connections is caused, first of all, by the possibility to obtain high superconducting transition temperature ( Tc ∼ 55K ) [1], which puts them on par with the cupper high-temperature materials. In this case, first of all, it is necessary to know their physical properties in standard conditions. In this context, the particular interest is the determination of kinetic coefficients, and study their dependence on temperature. Specifically, in the connections of YBa2Cu3O4 and La2-x (SrBa)xCuO4) we observe a number of anomalies in temperature dependence of the thermoelectric coefficient α and resistivity ρ. It is necessary to determine these values based on the actual electron density of states inherent in the quasi-two-dimensional systems. This definition allows us to compare the results with those obtained previously on the basis of the phenomenological approach [2], the temperature dependence of α and ρ in cupper compounds, as well as in new materials based on FeAs. In this paper the kinetic coefficients are calculated (of resistivity ρ and thermoelectric coefficient α) in systems with anisotropic quasi-energy spectrum. The basis of calculation laid the definition of these coefficients in accordance with the theory of Mott and Davis [3] and the expression for the density of electron states, which is the characteristic for quasi system with an anisotropic energy spectrum. A series of mathematical transformations are completed, that are convenient for numerical calculations. The temperature dependence of the quantities of ρ and α are studied for different values of the energy spectrum of the anisotropy parameter η = W2/W1 and the values of the occupation numbers n. A number of peculiarities in the behavior of these quantities as a function of temperature are identified. The main result of the study: by choosing the parameters n and η it is possible to provide the qualitative agreement between theory and experimental data as a hightemperature materials based on copper oxide and iron-based. In this context, as well as in the phenomenological approach, the narrow energy bands is an important condition. The theory is based on the fermi-liquid approach, because an important source is the fact of the narrowness of the energy bands, which provided strong electron correlations due to Coulomb interaction and polar effects.