Anomalous 4$f$ fine structure in TmSe${}_{1-x}$Te${}_x$ across the metal-insulator transition

Abstract

Hybridization between localized 4$f$ and itinerant 5$d$6$s$ states in heavy fermion compounds is a well-studied phenomenon and commonly captured by the paradigmatic Anderson model. However, the investigation of additional electronic interactions, beyond the standard Anderson model, has been limited, despite their predicted important role in the exotic quasiparticle formation in mixed-valence systems. We investigate the 4$f$ states in TmSe${}_{1-x}$Te${}_x$ throughout a semimetal-insulator phase transition, which drastically varies the interactions related to the 4$f$ states. Using synchrotron-based hard x-ray and extreme ultraviolet photoemission spectroscopy, we resolve subtle peak splitting in the 4$f$ peaks near the Fermi level in the mixed-valent semimetal phase. The separation is enhanced by several tens of meV by increasing the lattice parameter by a few percent. Our results elucidate the evolving nature of the 4$f$ state across the phase transition, and provide direct experimental evidence for electronic interactions beyond the standard Anderson model in mixed-valence systems.

5 pages, 4 figures for the main text, 6 pages and 5 figures for the supplementary

References in corpus (14)

• On the possibility of an excitonic insulator at the semiconductor-semimetal transition
• Quantum Oscillations of Electrical Resistivity in an Insulator
• Fermi surface in the absence of a Fermi liquid in the Kondo insulator SmB${}_6$
• Excitons in topological Kondo insulators - theory of thermodynamic and transport anomalies in SmB${}_6$
• Electron-phonon interaction and antiferromagnetic correlations
• Additional energy scale in SmB${}_6$ at low temperature
• Anomalous 3D bulk AC conduction within the Kondo gap of SmB${}_6$ single crystals
• Unusual high-field metal in a Kondo insulator
• Majoranas in mixed-valence insulators
• Topological properties and the dynamical crossover from mixed-valence to Kondo-lattice behavior in golden phase of SmS
• SmO thin films: a flexible route to correlated flat bands with nontrivial topology
• Valence effect on the thermopower of Eu systems
• Hybridization and Correlation between f- and d-orbital electrons in a valence fluctuating compound EuNi2P2
• Mixed-valence state in the dilute-impurity regime of La-substituted SmB${}_6$