Naslov
Relationship between the thermopower and entropy of strongly correlated electron systems

Autori
Zlatić, Veljko ; R. Monnier ; J. K. Freericks ; K. W. Becker

Izvornik
Physical Review B - Condensed Matter and Materials Physics (1098-0121) 76 (2007), 8; 085122-1

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

Ključne riječi
correlated systems; heat and charge transport; thermopower; entropy

Sažetak
A number of recent experiments report on a correlation between the low-temperature slope of the thermopower, α ∕ T, and the specific heat coefficient γ =CV∕ T for heavy fermions and valence fluctuating compounds with Ce, Eu, Yb, and U ions. Assuming that charge and heat currents at low temperatures are transported by quasiparticles, we first derive the universal value for the ratio q=α ∕ γ T using macroscopic transport equations. We then calculate the thermal response of the Fermi liquid (FL) regime of the periodic Anderson model and of the Falicov-Kimball model by dynamical mean field theory and find the q ratio. Eventually, we calculate the temperature dependence of α (T) above the FL regime using the “ poor man’ s” approach, which describes the scattering of conduction electrons on the lattice of f ions by the single impurity Anderson model with crystal field (CF) splitting. The overall temperature dependence is obtained by interpolating between the FL and the poor man’ s solution, and is explained in simple terms. The shape of α (T) is determined by the relative magnitude of the Kondo scale TK and the CF splitting. Pressure or doping (chemical pressure) affects α (T) by transforming the narrow Kondo resonances into a broad spectral function typical of valence fluctuators. This changes the effective degeneracy of the f state and results in a drastic modification of α (T). Temperature also changes the degeneracy of the f state by populating the excited CF states. Since TK is strongly pressure dependent, while the CF splitting is not, the shape of α (T) is a sensitive function of pressure or doping. These results explain the near universality of the q ratio and the overall behavior of α (T) in EuCu2(Ge1− xSix)2, CePt1− xNix, YbIn1− xAgxCu4, and similar systems.

Izvorni jezik
Engleski

Znanstvena područja
Fizika

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