Multiphase superconductivity in PdBi₂

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Materials

Background:

• Unconventional superconductivity typically involves magnetic correlations, as seen in cuprates and heavy fermion systems.
• Materials with strong spin-orbit coupling can exhibit complex superconducting phases and field-induced transitions.
• β-PdBi₂ is a layered, non-magnetic superconductor with potential for exotic superconducting states.

Purpose of the Study:

• To investigate the nature of superconductivity in β-PdBi₂ under an applied magnetic field.
• To explore the possibility of unconventional pairing mechanisms in this material.
• To reconcile conflicting experimental observations regarding superconducting gaps in β-PdBi₂.

Main Methods:

• Utilized tunnelling spectroscopy on thin β-PdBi₂ monocrystals.
• Fabricated planar superconductor-insulator-normal metal junctions.
• Applied in-plane magnetic fields and analyzed superconducting properties.

Main Results:

• Observed a distinct discontinuity in superconducting properties with increasing in-plane magnetic field.
• This discontinuity indicates a transition from conventional (s-wave) to nodal pairing.
• Theoretical analysis supports spin polarization and spin-momentum locking as driving factors.

Conclusions:

• A magnetic-field-driven phase transition to unconventional, possibly p-wave, pairing occurs in β-PdBi₂.
• The transition is attributed to broken inversion symmetry, spin polarization, and spin-momentum locking.
• This reconciles previous findings of single s-wave gaps with predictions of multigap superconductivity.