First-Order Structural Change Accompanied by Yb Valence Transition in YbInCu4

TL;DR

This study used high-energy x-ray diffraction to reveal a structural transition in YbInCu4 from cubic to tetragonal at the valence transition temperature, without accompanying valence ordering, suggesting involvement of electronic symmetries.

Contribution

It provides direct experimental evidence of a structural change without valence ordering in YbInCu4, highlighting the role of electronic symmetries beyond valence degrees of freedom.

Findings

Detection of Bragg peak splitting indicating structural change

Absence of superlattice reflections suggests no valence ordering

Structural transition involves symmetry change from cubic to tetragonal

Abstract

A diffraction experiment using a high energy x-ray was carried out on YbInCu4. Below the Yb valence transition temperature, the splitting of Bragg peaks was detected in higher-order reflections. No superlattice reflections accompanying the valence ordering were found below the transition temperature. These experimental findings indicate that a structural change from a cubic structure to a tetragonal structure without valence ordering occurs at the transition temperature. Such a structural change free from any valence ordering is difficult to understand only in terms of Yb valence degrees of freedom. This means that the structural change may be related to electronic symmetries such as quadrupolar degrees of freedom as well as the change in Yb valence.