Single crystal growth and physical characterization to fine tune YbIn1-xTxCu4 (T = Au, Ag) towards the critical endpoint of the valence transition

TL;DR

This study explores how Au and Ag substitutions in YbInCu4 influence its valence transition, revealing the critical endpoint's dependence on composition and growth conditions, with implications for understanding phase transitions in correlated electron systems.

Contribution

It provides a detailed phase diagram of YbInCu4 with various substitutions and demonstrates how defects and growth conditions affect the valence transition and critical endpoint.

Findings

The critical endpoint position varies with substitution type and growth conditions.

Multiple thermal cycles modify physical properties, indicating defect influence.

Substitutions can tune the valence transition towards the critical endpoint.

Abstract

Pure as well as Ag- and Au-substituted YbInCu$_4$ single crystals were structurally and chemically characterized and investigated by means of heat capacity, magnetization, resistivity and ultrasonic measurements. We studied the influence of different compositions of the initial melt as well as of Au and Ag substitutions on the valence change and investigated whether this change occurs via a first-order phase transition or via crossover. We constructed a phase diagram of YbInCu$_4$ as a function of various substitutions and show that the position of the critical endpoint of the valence transition depends on the substituent and on the conditions under which the samples were grown. Multiple thermal cycles through the first-order transition lead to a significant modification of the physical properties which clearly demonstrated the influence of defects in substituted YbInCu$_4$.