Topological nodal i-wave superconductivity in PtBi₂

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Materials

Background:

• Conventional superconductors exhibit electron pairing with high symmetry.
• Unconventional superconductors, like high-temperature cuprates, possess nodes in their superconducting gap, indicating d-wave symmetry.
• Topological materials offer unique electronic properties arising from their band structure.

Purpose of the Study:

• To investigate the superconducting properties of the Weyl semimetal PtBi2.
• To determine the pairing symmetry of superconductivity in PtBi2.
• To explore the potential of PtBi2 as a platform for topological phenomena, specifically Majorana bound states.

Main Methods:

• Angle-resolved photoemission spectroscopy (ARPES) was employed to probe the electronic structure of PtBi2.
• Superconducting gap nodes were identified using ARPES measurements.
• Theoretical calculations were performed to infer the emergence of Majorana flat bands.

Main Results:

• Nodes were observed in the superconducting gap of PtBi2 below 10 K, implying unconventional i-wave pairing symmetry.
• Superconductivity in PtBi2 gaps the topological surface states (Fermi arcs) while bulk states remain normal.
• The observed gap nodes are located at the center of the Fermi arcs, suggesting topologically protected Majorana cones.

Conclusions:

• PtBi2 is an unconventional, topological i-wave superconductor.
• The material's surface states host Majorana cones, leading to the theoretical prediction of robust zero-energy Majorana flat bands at surface step edges.
• PtBi2 presents a promising material platform for generating and manipulating Majorana bound states.