Naslov
Multiple temperature scales of the periodic Anderson model: Slave boson approach

Autori
Burdin, Sebastien ; Zlatić, Veljko

Izvornik
Physical Review B - Condensed Matter and Materials Physics (1098-0121) 79 (2009), 11; 115139-1

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

Ključne riječi
1st-order valence transition; Kondo-lattice; transport-properties; magnetic-impurities; YBInCu4; YBAl3

Sažetak
The thermodynamic and transport properties of intermetallic compounds with Ce, Eu, and Yb ions are discussed using the periodic Anderson model with an infinite correlation between f electrons. At high temperatures, these systems exhibit typical features that can be understood in terms of a single-impurity Anderson or Kondo model with Kondo scale TK. At low temperatures, one often finds a normal state governed by the Fermi liquid (FL) laws with characteristic energy scale T0. The slave boson solution of the periodic model shows that T0 and TK depend not only on the degeneracy and the splitting of the f states, the number of c and f electrons, and their coupling but also on the shape of the conduction-electrons density of states (c DOS) in the vicinity of the chemical potential &#181; . The ratio T0/TK depends on the details of the band structure which makes the crossover between the high- and low-temperature regimes system dependent. We show that the c DOS with a sharp peak close to &#181; yields T0<<TK, which explains the &#8220; slow crossover&#8221; observed in YbAl3 or YbMgCu4. The c DOS with a minimum or a pseudogap close to &#181; yields T0>>TK ; this leads to an abrupt transition between the high- and low-temperature regimes, as found in YbInCu4-like systems. In the case of CeCu2Ge2 and CeCu2Si2, where T0~=TK, we show that the pressure dependence of the T2 coefficient of the electrical resistance, A=rho(T)/T2, and the residual resistance are driven by the change in the degeneracy of the f states. The FL laws obtained for T<<T0 explain the correlation between the specific-heat coefficient gamma=CV/T and the thermopower slope alpha(T)/T or between gamma and the resistivity coefficient A. The FL laws also show that the Kadowaki-Woods ratio, RKW=A/gamma2, and the ratio q=lim{; ; ; T-->0}; ; ; alpha/gammaT assumes nonuniversal values due to different low-temperature degeneracies of various systems. The correlation effects can invalidate the Wiedemann-Franz law and lead to an enhancement of the thermoelectric figure of merit. They can also enhance (or reduce) the low-temperature response of the periodic Anderson model with respect to the predictions of a single-impurity model with the same high-temperature behavior as the periodic one.

Izvorni jezik
Engleski

Znanstvena područja
Fizika

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