Infrared dynamics of YbIn1−xAgxCu4: Kondo scaling, sum rules, and temperature dependence

We present an infrared/optical study of the dynamics of the strongly correlated electron system YbIn1−xAgxCu4 as a function of composition and temperature for x ranging from 0 to 1, and T between 20 and 300 K. YbIn1−xAgxCu4 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 1 and the infrared sum rule behavior, and provide a picture in which to view both the lowand high-energy x-dependent features of the infrared data.