Topologically trivial gap-filling in superconducting Fe(Se,Te) by one-dimensional defects

Area of Science:

• Materials Science
• Condensed Matter Physics
• Quantum Computing

Background:

• Structural distortions impact material properties at macro and nano scales.
• Nanoscale defects like domain walls are investigated for topological superconductivity and Majorana Fermions for quantum computing.

Purpose of the Study:

• To investigate the nature of purported domain walls in Fe(Se,Te) potentially hosting Majorana modes.
• To clarify the role of structural defects in the topological properties of Fe(Se,Te).

Main Methods:

• Utilized scanning tunneling microscopy to probe atomic lattice distortions.
• Employed electric fields to manipulate sub-surface impurities and observe lattice response.
• Analyzed superconducting properties of different 1D defect types.

Main Results:

• Atomic lattice displacement shifts at line defects are caused by sub-surface impurities warping the surface layers.
• Repositioning impurities directly visualized the lattice shift and defect-free regions.
• A distinct type of 1D defect showed fully gapped superconductivity, indicating trivial topology.

Conclusions:

• The observed 1D defects in Fe(Se,Te) are topologically trivial.
• Sub-surface impurities, not domain walls, are responsible for lattice distortions previously associated with topological superconductivity.