A strongly inhomogeneous superfluid in an iron-based superconductor

Area of Science:

• Condensed Matter Physics
• Materials Science
• Superconductivity

Background:

• Unconventional superconductors may exhibit spatial variations in their superfluid properties.
• The driving factors behind these potential inhomogeneities, such as disorder or scattering, remain unclear.

Purpose of the Study:

• To investigate the spatial variations of the superfluid in iron-based superconductors.
• To determine the relationship between superfluid inhomogeneity and other electronic/structural properties.

Main Methods:

• Utilized atomic-resolution Josephson scanning tunnelling microscopy.
• Simultaneously measured topographic and electronic properties of FeTe$_{0.55}$Se$_{0.45}$.

Main Results:

• Revealed a strongly inhomogeneous superfluid in FeTe$_{0.55}$Se$_{0.45}$.
• Found no correlation with structural disorder, strong inter-pocket scattering, or pair-breaking energy.
• Observed a direct spatial correlation between superfluid density and local quasiparticle strength.

Conclusions:

• Established the existence of strongly inhomogeneous superfluids in unconventional superconductors.
• Ruled out chemical disorder and inter-band scattering as primary causes of inhomogeneity.
• Highlighted the link between quasiparticle character and superfluid density, comparable to observations in copper oxides.