Theory of the first-order isostructural valence phase transitions in mixed valence compounds YbIn_{x}Ag_{1-x}Cu_{4}

Abstract

For describing the first-order isostructural valence phase transition in mixed valence compounds we develop a new approach based on the lattice Anderson model. We take into account the Coulomb interaction between localized f and conduction band electrons and two mechanisms of electron-lattice coupling. One is related to the volume dependence of the hybridization. The other is related to local deformations produced by f- shell size fluctuations accompanying valence fluctuations. The large f -state degeneracy allows us to use the 1/N expansion method. Within the model we develop a mean-field theory for the first-order valence phase transition in YbInCu_{4}. It is shown that the Coulomb interaction enhances the exchange interaction between f and conduction band electron spins and is the driving force of the phase transition. A comparison between the theoretical calculations and experimental measurements of the valence change, susceptibility, specific heat, entropy, elastic constants and volume change in YbInCu_{4} and YbAgCu_{4} are presented, and a good quantitative agreement is found. On the basis of the model we describe the evolution from the first-order valence phase transition to the continuous transition into the heavy-fermion ground state in the series of compounds YbIn_{1-x}Ag_{x}Cu_{4}. The effect of pressure on physical properties of YbInCu_{4} is studied and the H-T phase diagram is found.

17 pages RevTeX, 9 Postscript figures, to be submitted to Phys.Rev. B

References in corpus (4)

• Topological approach to Luttinger's theorem and the Fermi surface of a Kondo lattice
• Coherence scale of the Kondo lattice
• Optical study of the electronic phase transition of strongly correlated YbInCu_4
• Evidence for exhaustion in the conductivity of the infinite-dimensional periodic Anderson model

Cited by in corpus (5)

• Valence Fluctuations Revealed by Magnetic Field Scan: Comparison with Experiments in YbXCu_4 (X=In, Ag, Cd) and CeYIn_5 (Y=Ir, Rh)
• Two-fluid behavior of the Kondo lattice in the 1/N slave boson approach
• Competing chiral and multipolar electric phases in the extended Falicov-Kimball model
• Hybridization and Correlation between f- and d-orbital electrons in a valence fluctuating compound EuNi2P2
• Valence transition in topological Kondo insulator