Superconductivity in topological insulatorβ-PdBi₂under pressure

Area of Science:

• Condensed Matter Physics
• Materials Science
• Topological Materials

Background:

• Topological insulators like PdBi₂ possess unique electronic properties.
• PdBi₂ exists in two phases (α and β) with distinct behaviors under pressure.
• The pressure-dependent properties of β-PdBi₂, particularly its superconductivity, remain under-explored.

Purpose of the Study:

• To investigate the crystal structure and superconductivity of β-PdBi₂ under varying pressures.
• To determine the stability and superconducting transition temperature (T_c) of β-PdBi₂ from 0 to 22.0 GPa.
• To elucidate the mechanism behind the observed superconductivity in β-PdBi₂.

Main Methods:

• Synchrotron X-ray diffraction (XRD) for structural analysis under pressure.
• Temperature-dependent measurements to determine superconducting transition temperatures (T_c).
• Analysis of upper critical field behavior to understand superconducting mechanisms.

Main Results:

• β-PdBi₂ exhibits superconductivity with T_c up to 4.10 K at ambient pressure in a tetragonal structure (I4/mmm).
• No structural phase transitions were observed in β-PdBi₂ up to 22.0 GPa; unit cell volume decreased monotonically.
• Superconductivity in β-PdBi₂ was observed up to 11.8 GPa with a nearly constant T_c of ~4.4 K.
• The superconductivity mechanism is likely an s-wave clean or p-wave polar model, not a simple s-wave dirty limit.

Conclusions:

• β-PdBi₂ is a pressure-stable topological insulator with robust superconductivity.
• The α-PdBi₂ phase transforms into the β-PdBi₂ phase under pressure.
• This study provides the first systematic investigation of superconductivity in β-PdBi₂ under pressure, offering insights into its electronic behavior.