Observation of a new excitation in the mixed-valent state of YbInCu_4

TL;DR

This study uses infrared spectroscopy to investigate YbInCu_4, revealing new resonances in its mixed-valent state that could shed light on its electronic properties and the nature of the Kondo state.

Contribution

It reports the observation of sharp resonances at 0 and 0.25 eV in the mixed-valent state of YbInCu_4, providing new insights into its electronic excitations.

Findings

Spectral weight decreases with temperature up to 1.5 eV

Sharp resonances at 0 and 0.25 eV in the mixed-valent state

Resonances may be key to understanding the Kondo state

Abstract

Infrared measurements are used to obtain conductivity as a function of temperature and frequency in YbInCu_4, which exhibits an isostructural transition to a mixed-valent state at T_v \simeq 42 K. In addition to a gradual loss of spectral weight with decreasing temperature extending up to 1.5 eV, sharp resonances appear in the mixed-valent state at 0 and 0.25 eV . These features may be key to understanding both YbInCu_4 and the nature of the mixed-valent Kondo state.