Theoretical interpretation of optical conductivity of YbCu4Ag,Au

Abstract

We focus on YbCu4Ag and YbCu4Au and interpret the optical conductivity, measured from 2 meV to 6 eV at 10 and 300 K, in terms of self-consistent electronic structure calculations. Most of the relevant spectral structures are interpreted as interband transitions from hybridized f–d states below and at the Fermi level at high symmetry points. In particular, the large shoulder at about 2.4 and 2 eV in the spectrum of YbCu4Au and YbCu4Ag, respectively, can be interpreted in terms of a transition Γ4→Γ3 involving mostly d states. We also compare the electronic structure of YbCu4Ag with that of LuCu4Ag, to ascertain the influence of the f states on the conduction bands and carrier density at EF. This allows us to draw some qualitative considerations on the f-band hybridization in these compounds.