Relationship between the thermopower and entropy of strongly correlated electron systems

Abstract

A number of recent experiments report the low-temperature thermopower α and specific heat coefficients γ = CV /T of strongly correlated electron systems. Describing the charge and heat transport in a thermoelectric by transport equations, and assuming that the charge current and the heat current densities are proportional to the number density of the charge carriers, we obtain a simple mean-field relationship between α and the entropy density S of the charge carriers. We discuss corrections to this mean-field formula and use results obtained for the periodic Anderson and the Falicov-Kimball models to explain the concentration (chemical pressure) and temperature dependence of α/γT in EuCu2(Ge1−xSix)2, CePt1−xNix, and YbIn1−xAgxCu4 intermetallic compounds. We also show, using the 'poor man's mapping' which approximates the periodic Anderson lattice by the single impurity Anderson model, that the seemingly complicated behavior of α(T ) can be explained in simple terms and that the temperature dependence of α(T ) at each doping level is consistent with the magnetic character of 4f ions.

Scaling behavior of the thermopower of the archetypal heavy-fermion metal YbRh2Si2

“…On the basis of the Fermi liquid theory description, the term in the brackets on the right hand side of Eq. (1) can be simplified, so that one has S/T ∝ N (ε = µ) ∝ C/T ∝ M * at T → 0 [10][11][12][13]. As a result, upon taking into account that charge and heat currents at low temperatures are transported by quasiparticles, the ratio…”

“…Indeed, S/T is sensitive to the derivative of the density of electronic states and the change in the relaxation time at µ [9,10]. Using the Boltzmann equation, the thermopower S/T can be written as [9][10][11][12][13] …”

“…where S ent the entropy density of charge carriers [10][11][12][13]. Thus, we expect that within FC theory one can obtain an adequate description of the thermopower and its scaling behavior, for the theory is based on the quasiparticle paradigm [3,4,[14][15][16].…”

Crossover between Fermi liquid and non-Fermi liquid behavior in the non-centrosymmetric compound Yb2Ni12P7

“…A FL state can be characterized by the ratio of S 0 (T )/T to γ. [50,52,53] A "quasi-universal" ratio, q = (N A e/γ)(S 0 /T ) ≈ ±1, is expected to be obeyed for FL systems where N A is Avogadro's number and e is the charge of an electron. The sign of q depends on the dominant type of charge carriers.…”

Signatures of quantum criticality in the thermopower of Ba(Fe1−xCox)2Arsenijević1, Hodovanets2, Gáal3 et al. 2013Phys. Rev. B331320View full textAdd to dashboardCite

“…It can be interpreted as the entropy per charge carrier [19,20]. S can be used to detect deviations from the Landau Fermiliquid (FL) picture, i.e.…”