High temperature heaviness in CeCoIn$_5$

The temperature-dependent evolution of the Kondo lattice is a long-standing topic of theoretical and experimental investigation and yet it lacks a truly microscopic description of the relation of the basic $f-d$ hybridization processes to the fundamental $T$ scales of Kondo screening and Fermi-liquid lattice coherence. The $T$-dependence of $f-d$ hybridization dispersions and $f$ spectral weight in the Kondo lattice system CeCoIn$_5$ is investigated using $f$-resonant angle-resolved photoemission (ARPES) with comparison to first principles dynamical mean field theory (DMFT) calculations. Three different $f-d$ hybridization scenarios at different $k$-locations of the Fermi surface(FS) are measured from two orthogonal (001) and (100) cleaved surfaces. In contrast to a commonly accepted belief that $f-d$ hybridization occurs only below the lattice coherence temperature of $T^*$ $\sim$ 45 K, ARPES, in agreement with DMFT, reveals $f$ participation in the FS at temperatures much higher than $T^*$, well into the incoherent partial-screening regime of logarithmic Kondo-coupling spin-flip scattering.