Electronic and Structural Properties of Yb-based Materials

We have investigated the electronic, structural, and optical spectroscopy of YbT₂Zn₂₀-based (T = Co, Rh, and Ir) 1-2-20 compounds using first-principles calculations that account for the strong on-site-f-electron Coulomb interactions. We observed the strong hybridization and screening of the f-levels by the itinerant conduction electrons that led to massive electron behavior with an unenhanced electronic Sommerfeld coefficient of over ~600 mJ mol^-1 K^-2. The optical spectroscopy exhibits renormalized Drude response, a partial enhancement of the dynamical conductivity below ~1.0 eV, the emergence of the midinfrared peak structures at ~0.46 eV, and low photon-energy dynamical effective mass and scattering rate with nontrivial energy-dependent scattering resonances from free carriers. Surprisingly, both the electronic and optical spectroscopy of YbT₂Zn₂₀ are distinctly different from the rest of the studied materials, with characteristic features that support its closeness to quantum criticality.