Naslov
Dielectric properties of multiband electron systems: I - Tight-binding formulation

Autori
Županović, Paško ; Bjeliš, Aleksa ; Barišić, Slaven

Izvornik
Zeitschrift für Physik B (0722-3277) 101 (1996); 387-396

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
dielectric matrix; random phase approximation; self-polarization corrections

Sažetak
The screened electron-electron interaction in a multi-band electron system is calculated within the random phase approximation and in the tight-binding representation. The obtained dielectric matrix contains, beside the usual site-site correlations, also the site-bond and bond-bond correlations, and thus includes all physically relevant polarization processes. The arguments are given that the bond contributions are negligible in the long wavelength limit. We analyse the system with two non-overlapping bands in this limit, and show that the corresponding dielectric matrix reduces to a 2x2 form. The intra-band and inter-band contributions are represented by diagonal matrix elements, while the off-diagonal elements contain the mixing between them. The latter is absent in insulators but may be finite in conductors. Performing the multipole expansion of the bare long-range interaction, we show that this mixing is directly related to the symmetry of the atomic orbitals participating in the tight-binding electronic states. In systems with forbidden atomic dipolar transitions, the intra-band and inter-band polarizations are separated. However, when the dipolar transitions are allowed, the off-diagonal elements of the dielectric matrix are of the same order as diagonal ones due to a finite monopole-dipole interaction between the intra-band and inter-band charge fluctuations.

Izvorni jezik
Engleski

Znanstvena područja
Fizika

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