Visualizing the Odd-Parity Superconducting Order Parameter and Its Quasiparticle Surface Band in UTe₂

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Materials

Background:

• Topological superconductivity is a quantum state with exotic properties.
• Intrinsic topological superconductivity (ITS) requires specific order parameters.
• Identifying ITS in materials like UTe2 is crucial for understanding novel quantum phenomena.

Purpose of the Study:

• To experimentally identify and characterize intrinsic topological superconductivity (ITS) in UTe2.
• To distinguish between chiral and non-chiral ITS order parameters using surface-sensitive techniques.
• To investigate the nature of the topological quasiparticle surface band (QSB) in UTe2.

Main Methods:

• Utilized s-wave superconductive scan-tip scanning tunneling microscopy (STM) for high-resolution surface imaging.
• Employed Andreev spectroscopy to probe the electronic states at the superconductor-insulator interface.
• Performed quasiparticle interference (QPI) imaging to map the dispersion of surface states.

Main Results:

• Observed an intense zero-energy Andreev conductance maximum at the UTe2 (0-11) surface, indicative of a QSB.
• Demonstrated that the superconductivity in UTe2 is non-chiral, evidenced by the evolution of the Andreev peak.
• Visualized QPI patterns of the QSB, revealing a characteristic sextet of interference wavevectors within the superconducting gap.

Conclusions:

• The experimental findings strongly support a non-chiral, spin-triplet, time-reversal conserving, odd-parity, a-axis nodal, B3u symmetry for the bulk superconducting order parameter in UTe2.
• The identified topological quasiparticle surface band (QSB) serves as a key identifier for nodal intrinsic topological superconductivity (ITS).
• This work provides critical experimental evidence for topological superconductivity in UTe2, opening avenues for future research in topological quantum computation.