Special Condensed Matter Seminar

The temperature-dependence of f-d hybridized band dispersions and Fermi-energy f spectral weight in the Kondo lattice system CeCoIn5 is investigated using f-resonant angle-resolved photoemission (ARPES) with sufficient detail to allow direct comparison to first principles dynamical mean field theory (DFT+DMFT) calculations containing full realism of crystalline electric field (CEF) states. The low T ARPES results, for two orthogonal (001) and (100) cleaved surfaces, show the counterintuitive result that features peculiar to the localized f-electron 3D Fermi surface found in DFT calculations nonetheless display clear itinerant felectron participation, consistent with the low energy scale description of DFT+DMFT. Also the ARPES T dependence of three different f-d hybridization scenarios, with additional microscopic insight provided by DMFT, reveal f participation in the Fermi surface at temperatures much higher than the lattice coherence temperature, T ≈ 45 K, commonly believed to be the onset for such behavior. The observation of a T-dependent CEF degeneracy crossover in the DMFT theory, below T, is specifically highlighted.