Pressure-induced quantum phase transitions in topological insulator YbB6

TL;DR

This study investigates pressure-induced quantum phase transitions in the topological insulator YbB6, revealing two distinct insulating phases separated by a metallic state, driven by valence changes in Yb f-orbitals, and highlighting the tunability of its topological properties.

Contribution

First experimental observation of pressure-induced quantum phase transitions in YbB6, linking topological states to valence changes and hybridization effects.

Findings

Two pressure-induced quantum phase transitions observed.

Insulating phases separated by a metallic phase due to valence change.

Different topological origins for the two insulating states.

Abstract

Topological insulators (TIs) containing 4f electrons have recently attracted intensive interests due to the possible interplay of their non-trivial topological properties and strong electronic correlations. YbB6 and SmB6 are the prototypical systems with such unusual properties, which may be tuned by external pressure to give rise to new emergent phenomena. Here, we report the first observation, through in-situ high pressure resistance, Hall, X-ray diffraction and X-ray absorption measurements, of two pressure-induced quantum phase transitions (QPTs) in YbB6. Our data revealthat the two insulating phases are separated by a metallic phase due to the pressure-driven valence change of Yb f-orbitals. In combination with previous studies, our results suggest that the two insulating states may be topologically different in nature and originate from the d-p and d-f hybridization, respectively. The tunable topological properties of YbB6 revealed in this study may shed light on the intriguing correlation between the topology and the 4f electrons from the perspective of pressure dependent studies.