Hybridization and Slow Coherence Crossover in the Intermediate Valence Compound YbAl$_3$ via Quasiparticle Scattering Spectroscopy

TL;DR

This study uses quasiparticle scattering spectroscopy to reveal the temperature-dependent hybridization process in YbAl$_3$, identifying a new high-temperature scale and providing insights into the formation of a coherent Fermi liquid.

Contribution

The paper introduces a novel spectroscopic approach to pinpoint the onset of hybridization and coherence in YbAl$_3$, highlighting a higher temperature scale than previously recognized.

Findings

Hybridization begins around 110 K, higher than the coherence temperature.

The indirect hybridization gap opens with the emergence of a coherent Fermi liquid.

A new high-temperature scale for hybridization was identified.

Abstract

The intermediate valence compound YbAl$_3$ is known to undergo a hybridization process between itinerant and localized electrons. The resulting heavy Fermi liquid remains non-magnetic and non-superconducting. A microscopic understanding of the hybridization process in YbAl$_3$ is still lacking although some characteristic temperature and energy scales have been identified. Here we report results from novel spectroscopic measurements based on quasiparticle scattering. From the conductance spectra taken over a wide temperature range, we deduce that the band renormalization and hybridization process begins around 110 K, causing the conductance enhancement with a Fano background. This temperature, a new scale found in this work, is much higher than the coherence temperature (34 K). Our observation is in agreement with the slow crossover scenario discussed recently in the literature. The indirect hybridization gap appears to open concomitantly with the emergence of a coherent Fermi liquid. Thus, we suggest its measurement as a more rigorous way to define the coherence temperature than just taking the temperature for a resistivity peak.