Pressure-induced anomalous valence crossover in cubic YbCu₅-based compounds.

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Materials

Background:

• Heavy fermion systems are crucial for understanding complex electronic behaviors.
• YbCu5-based compounds are archetypal cubic systems exhibiting unique properties.
• Understanding valence states under pressure is key to novel material design.

Purpose of the Study:

• Investigate the pressure-induced valence crossover in YbCu5-based heavy fermion systems.
• Clarify the anomalous valence behavior not predicted by conventional theories.
• Compare findings with Yb2Pd2Sn to disprove specific high-pressure state scenarios.

Main Methods:

• High-pressure experiments on YbCu5 and Yb2Pd2Sn.
• Analysis of Ytterbium (Yb) valence changes under varying pressure.
• Comparative study of valence behavior across different Yb-based intermetallics.

Main Results:

• Observed a pressure-induced anomalous valence crossover in YbCu5 without structural phase transition.
• Yb valence decreases with increasing pressure, shifting from localized 4f13 to valence fluctuation.
• Yb valence in Yb2Pd2Sn increases monotonically with pressure, disproving a reentrant Yb2+ state.

Conclusions:

• YbCu5-based compounds display unique valence behavior under pressure, deviating from standard c-f hybridization models.
• The study refutes the possibility of a reentrant non-magnetic Yb2+ state in Yb2Pd2Sn at high pressure.
• Highlights the singular nature of Yb valence crossover in compressed Yb-based intermetallics.