Monolayer FeSe epitaxially grown on SrTiO3 substrate exhibits one of the highest superconducting transition temperatures of the iron-based superconductors but the origins of its superconductivity are still under debate. Here, the authors investigate the nature of the Cooper pairs using scanning tunnelling microscopy/spectroscopy and reveal evidence which supports sign changing pairing symmetry.
- Huimin Zhang
- Zhuozhi Ge
- Lian Li
