| AVS 66th International Symposium & Exhibition | |
| 2D Materials | Tuesday Sessions |
| Session 2D+EM+MI+MN+NS+QS-TuM |
| Session: | Novel Quantum Phenomena |
| Presenter: | Huimin Zhang, West Virginia University |
| Authors: | H. Zhang, West Virginia University Z. Ge, University of Wisconsin M. Weinert, University of Wisconsin L.L. Li, West Virginia University |
| Correspondent: | Click to Email |
Single layer FeSe film epitaxially grown on SrTiO3(001) substrate has drawn much interest for its novel interfacial effects, which have led to the highest superconducting temperature (TC) to date amongst all Fe-based superconductors. While several paring states, such as sign-persevering s++-wave, sign-changing nodeless d-wave and s±-wave have been suggested, the pairing symmetry remains to be experimentally validated. Here we investigate the intrinsic impurity-induced in-gap bound states and quasiparticle interference (QPI) patterns in single layer FeSe/SrTiO3 by scanning tunneling microscopy/spectroscopy. We observed bound states induced by nonmagnetic impurities, which strongly suggests a sign-changing order parameter. Through detailed analysis of the phase-sensitive QPI patterns, we further confirm that the order parameter indeed changes sign within the electron pockets. This identification of a sign change pairing symmetry in single layer FeSe/SrTiO3 presents a critical step towards the understanding of its high Tc superconductivity.