Evolution of the Kondo lattice electronic structure above the transport coherence temperature

Abstract

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-c hybridization processes to the fundamental temperature scales of Kondo screening and Fermi-liquid lattice coherence. Here, the temperature dependence of f-c hybridized band dispersions and Fermi-energy f spectral weight in the Kondo lattice system CeCoIn5 is investigated using f-resonant angle-resolved photoemission spectroscopy (ARPES) with sufficient detail to allow direct comparison to first-principles dynamical mean-field theory (DMFT) calculations containing full realism of crystalline electric-field states. The ARPES results, for two orthogonal (001) and (100) cleaved surfaces and three different f-c hybridization configurations, 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 DMFT results show the role of crystalline electric-field (CEF) splittings in this behavior and a T-dependent CEF degeneracy crossover below T* is specifically highlighted. A recent ARPES report of low T Luttinger theorem failure for CeCoIn5 is shown to be unjustified by current ARPES data and is not found in the theory.

Colloquium : Heavy-electron quantum criticality and single-particle spectroscopy

“…This is consistent with T hyb 0 ≈ 160K in this compound, see Table I. High-resolution ARPES results on CeCoIn 5 that are largely compatible with those of Chen et al (Chen et al, 2017) have also been reported by Jang et al (Jang et al, 2017). Though ARPES measurements on heavy-electron compounds have been a major experimental achievement, care has to be taken when extrapolating to the hightemperature region where the 4f electrons have to be localized across the phase diagram, as argued above.…”

Anisotropic c−f Hybridization in the Ferromagnetic Quantum Critical Metal CeRh6Ge4Wu1, Zhang2, Du3 et al. 2021Phys. Rev. Lett.333160View full textAdd to dashboardCite

“…This is consistent with the onset of c − f hybridization at high temperature obtained from a recent ultrafast optical pump-probe measurement [26]. This behavior is also similar to other HF compounds, e.g., CeCoIn 5 [27,28], and it could be attributed to Kondo screening involving CEF excitations [27][28][29][30]. Analysis of the magnetic susceptibility and inelastic neutron scattering suggests that the first excited CEF doublet in CeRh 6 Ge 4 lies at ∼6 meV above the ground-state doublet and it hybridizes strongly with the conduction bands [31].…”

“…The uncertainty of V is ∼ AE 10 meV along k y and slightly larger along k x due to weaker bands with smaller bending. Another source of uncertainty in the estimation of V is related to the RC-FDD division: since the ARPES energy resolution (∼20 meV) is larger than 4k B T, the recovered 4f bands above E F could be pushed slightly above the real positions [28], resulting in possible inaccuracy in V. However, since V along k y is much larger than the possible energy shift, this complication should not affect our main conclusion: V is obviously larger along k y compared to along k x . Such an anisotropic V is also manifested in the raw data via the presence The momentum anisotropy in V can be attributed to the crystal structure: the c − f hybridization should be dominated by electronic couplings between Ce and 12 nearest neighbor Rh and Ge atoms, which form small hexagons in the a − b plane halfway between Ce atoms along the chains.…”

Evidence for a delocalization quantum phase transition without symmetry breaking in CeCoIn 5

“…One way to view f-electron delocalization is as a result of Kondo hybridization between the f level and conduction electrons. Although there are reports of hybridization developing below about 45 Kelvin in pure CeCoIn5 (27) and Cd-doped Ce-CoIn5 (32) resulting in a detectable f-electron contribution to the Fermi surface, we find that the low-temperature carrier density of these materials is consistent with predominantly localized f-electrons (Fig. 1).…”