Evidence for d-wave superconductivity in single layer FeSe/SrTiO3 probed by quasiparticle scattering off step edges

Abstract

The de Gennes extrapolation length is a direction dependent measure of the spatial evolution of the pairing gap near the boundary of a superconductor, and thus provides a viable means to probe its symmetry. It is expected to be infinite and isotropic for plain s-wave pairing, and finite and anisotropic for d-wave. Here, we synthesize single layer FeSe films on SrTiO3(001) (STO) substrates by molecular beam epitaxy, and measure the de Gennes extrapolation length by scanning tunneling microscopy/spectroscopy. We find a 40% reduction of the superconducting gap near specular [110]Fe edges, yielding an extrapolation length of 8.0 nm. However, near specular [010]Fe edges the extrapolation length is nearly infinite. These findings are consistent with a phase changing pairing with 2-fold symmetry, indicating d-wave superconductivity. This is further supported by the presence of in-gap states near the specular [110]Fe edges, but not the [010]Fe edges. This work provides direct experimental evidence for d-wave superconductivity in single layer FeSe/STO, and demonstrates quasiparticle scattering at boundaries to be a viable phase sensitive probe of pairing symmetry in Fe-based superconductors.

18 pages, 4 figures

References in corpus (7)

• High-temperature superconductivity in iron-based materials
• Superconductivity in single-layer films of FeSe with a transition temperature above 100 K
• d-wave pairing from spin fluctuations in the KxFe{2-y}Se2 superconductors
• Monolayer FeSe on SrTiO${}_3$
• Visualizing landscapes of the superconducting gap in heterogeneous superconductor thin films: geometric influences on proximity effects
• Resilient nodeless $d$-wave superconductivity in monolayer FeSe
• An extensive impurity-scattering study on the pairing symmetry of monolayer FeSe films on SrTiO3

Cited by in corpus (12)

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• Eliashberg theory for spin-fluctuations mediated superconductivity -- Application to bulk and monolayer FeSe
• High-Temperature Majorana Fermions in Magnet-Superconductor Hybrid Systems
• Multichannel superconductivity of monolayer FeSe on SrTiO${}_3$: Interplay of spin fluctuations and electron-phonon interaction
• Tomonaga Luttinger liquid in the topological edge channel of multilayer FeSe
• In-situ topotactic chemical reaction for spectroscopies
• Capping layer influence and isotropic in-plane upper critical field of the superconductivity at the FeSe/SrTiO3 interface
• Dynamical Coulomb Blockade as a Signature of the Sign-Reversing Cooper Pairing Potential
• Fragile pressure-induced magnetism in FeSe superconductors with a thickness reduction