# Theory ties Fe d_xy orbital in monolayer FeSe/SrTiO3 to nodeless d-wave superconductivity

- Published: 2026-11-06 05:23 UTC
- Section: Science › Physics
- Tags: monolayer FeSe, FeSe on SrTiO3, d-wave superconductivity, Fe d_xy orbital, Josephson scanning tunneling microscopy, iron-based superconductors, pairing symmetry, kinetic frustration, quasiparticle interference, electron-only Fermi surface
- URL: https://realtech.media/news/rt-682773c056b9265398701637_theory_ties_fe/

**A preprint builds a multiorbital model of monolayer FeSe fitted to QPI and ARPES data. It favors d-wave pairing and predicts distinct Josephson STM patterns.**

![Theory ties Fe d_xy orbital in monolayer FeSe/SrTiO3 to nodeless d-wave superconductivity](https://sgzwpqqelzmajkcubgkl.supabase.co/storage/v1/object/public/rt-media/2026/11/972945db8256c2b5.jpg)
*Rickinasia, Wikimedia Commons, CC BY-SA 4.0*

A theoretical study of monolayer FeSe on SrTiO3 has been posted as an arXiv · preprint and has not yet been peer reviewed. The system shows high-temperature superconductivity with an electron-only Fermi surface. The authors use an experimentally constrained multiorbital theory to examine the role of the Fe d_xy orbital. They were motivated by recent Josephson scanning tunneling microscopy (JSTM) evidence for nodeless d-wave superconductivity in this material [1].

## Orbital structure and hopping

The authors constructed a tight-binding model that includes all five Fe orbitals in the physical two-Fe unit cell. It is fitted to quasiparticle interference (QPI) and angle-resolved photoemission spectroscopy (ARPES) data and reproduces the observed low-energy dispersions and electron-pocket structure [1].

The model shows substantial d_xy character near the Fermi level. The extracted hopping parameters are dominated by nearest-neighbor hopping [1]. This differs from the conventional picture of iron-based superconductors, where kinetic frustration suppresses nearest-neighbor hopping of the d_xy orbital and next-nearest-neighbor hopping dominates. According to the authors, this frustration is substantially lifted in monolayer FeSe.

The band structure also differs from the bulk-like ordering. The orbital ordering of the doublets is reversed, and together with interorbital hybridization this reconstructs the low-energy bands. The resulting electron pockets carry substantial d_xy weight [1].

## Pairing and Josephson signatures

The authors compared pairing channels with two approaches: itinerant spin-fluctuation calculations and strong-coupling exchange approaches. Both favor a robust d-wave pairing state. Its interband pairing components allow a fully gapped quasiparticle spectrum [1].

The study also derives a symmetry-based selection rule for spatial Josephson tunneling. It predicts bond-centered maxima and interference zeros enforced by mirror symmetry. These features distinguish d-wave pairing from competing s-wave states [1].

The symmetry-enforced nodal lines survive near Fe-site impurities. Around vortices the mirror protection is lost, but a pronounced contrast between the d- and s-wave Josephson patterns persists, according to the authors [1]. They conclude that the d_xy electronic structure is connected to nodeless d-wave superconductivity and that spatial Josephson interference can resolve pairing symmetry in multiorbital superconductors.

## Sources

1. [arXiv · препринт](https://arxiv.org/abs/2611.08037v1)

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Source: RealTech, realtech.media — https://realtech.media/news/rt-682773c056b9265398701637_theory_ties_fe/