Kondo interactions from band reconstruction in YbInCu(4)

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Magnetism

Background:

• Ytterbium Indium Copper (YbInCu4) exhibits a first-order valence transition at approximately 42 Kelvin.
• This transition is associated with a significant increase in Kondo temperature and valence fluctuations.
• Understanding the interplay between electronic structure and valence transitions is crucial for correlated electron systems.

Purpose of the Study:

• To investigate the electronic structure changes driving the valence transition in YbInCu4.
• To establish a link between the low-energy Kondo scale and higher-energy electronic properties.
• To provide experimental evidence for the role of electronic structure instability.

Main Methods:

• Utilized resonant inelastic x-ray scattering (RIXS) for bulk-sensitive, element-specific measurements.
• Performed theoretical model calculations to interpret the experimental spectra.
• Analyzed valence-projected charge excitation spectra.

Main Results:

• Observed an unusual quasigap in the Ytterbium-derived electronic state density below the transition.
• This quasigap was identified as a key factor destabilizing the electronic structure.
• The findings indicate renormalization of the low-energy effective Hamiltonian at the transition.

Conclusions:

• The study provides experimental evidence connecting temperature-driven changes in the Kondo scale to the electronic structure.
• The quasigap in the Yb-derived state density plays a critical role in the valence transition mechanism.
• This work advances the understanding of electronic instabilities in Kondo lattice systems.