UC Irvine

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.