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Landau Theory for Pair Density Modulation in Fe(Te,Se) Flakes
Po-Jui Chen1, Piers Coleman1,2
1Rutgers University, Department of Physics and Astronomy, Piscataway, New Jersey 08854, USA.
Physical Review Letters
|July 23, 2026
Summary
A new Landau theory explains pair-density modulation (PDM) in FeTe0.55Se0.45 flakes. This suggests local, iron-atom pairing in superconductors, potentially driven by Hunds coupling, offering testable predictions for scanning tunneling microscopy experiments.
Area of Science:
- Condensed Matter Physics
- Superconductivity
- Materials Science
Background:
- Recent scanning tunneling microscopy (STM) experiments observed pair-density modulation (PDM) in FeTe0.55Se0.45 flakes.
- Understanding the physical origin of PDM is crucial for advancing the study of iron-based superconductors.
Purpose of the Study:
- To develop a Landau theory explaining the observed pair-density modulation (PDM) in FeTe0.55Se0.45 flakes.
- To elucidate the symmetry constraints and pairing mechanisms underlying PDM in thin superconducting flakes.
Main Methods:
- Development of a Landau theory incorporating screw and glide symmetries.
- Analysis of PDM as a hybridized state of two order parameters with opposite glide and screw parity.
- Investigation of symmetry breaking at the surface and its effect on PDM stabilization.
Main Results:
- PDM is interpreted as a hybridized state of order parameters with opposite glide and screw parity.
- Surface glide symmetry breaking stabilizes PDM in thin flakes, explaining its absence in bulk.
- The symmetry constraints favor a site-based, rather than bond-based, pairing mechanism, suggesting local pairing at iron atoms.
Conclusions:
- The discovery of PDM in superconducting flakes points towards local pairing in iron-based superconductors, possibly driven by Hunds coupling.
- Predicted magnetic-field enhancement of PDM at low fields and a reentrant triplet phase at high fields, offering experimental verification avenues via STM.
