The Kondo Dynamics of YbIn(1-x)AgxCu4

We present an infrared/optical study of the dynamics of the strongly correlated electron system YbIn(1-x)AgxCu4 as a function of doping and temperature for x ranging from 0 to 1, and T between 20 and 300 K. This study reveals information about the unusual phase transition as well as the phases themselves. Scaling relations emerge from the data and are investigated in detail using a periodic Anderson model based calculation. We also provide a picture in which to view both the low and high-energy x-dependent features of the infrared data, including identification of high energy, temperature dependent features.Comment: 12 pages, 11 figures, submitted Phys. Rev.

Optically probing the Kondo resonance in YbIn1-xAg xCu4

We report the infrared charge dynamics of YbIn1-xAgxCu4 in a series of x- and T-dependent reflectivity measurements. Within the low-temperature coherent phase, characteristics of a low energy (0.25 eV) excitation appear to be controlled by the same Kondo scale, TK, which is relevant to the magnetic response (Phys. Rev. B 56 (1997) 7993). We show that the observed TK dependence of the frequency and strength of this excitation is consistent with an interpretation in terms of a coherent-to-incoherent quasiparticle transition between the correlation-induced bands of the periodic Anderson model (Phys. Rev. Lett. 92 (2004) 186405). Additionally, we consider an interpretation of x-dependence in the higher frequency optical response in terms of a rigid band structure picture where the filling is depleted by Ag doping, augmented by a Kondo resonance which tracks the x-dependent Fermi level. In addition to the properties of the low-temperature phase, our results also encompass the anomalous temperature dependent behavior in the vicinity of the electronic phase transition at low doping (x<0.3). © 2005 Elsevier B.V. All rights reserved

Infrared dynamics of YbIn1-x Agx Cu4: Kondo scaling, sum rules, and temperature dependence

We present an infrared/optical study of the dynamics of the strongly correlated electron system YbIn1-x Agx Cu4 as a function of composition and temperature for x ranging from 0 to 1, and T between 20 and 300 K. YbIn1-x Agx Cu4 evolves from a mixed-valent system at low x to a heavy-Fermion system at high x, and exhibits an unusual electronic phase transition in the low x region. This paper reveals information about the unusual phase transition as well as the phases themselves. Scaling relations emerge from the data and are investigated in detail using a periodic Anderson model based calculation. We also explore the temperature dependence of σ1 (ω) and the infrared sum rule behavior, and provide a picture in which to view both the low- and high-energy x -dependent features of the infrared data. © 2006 The American Physical Society