Simultaneous transport and tunneling spectroscopy of moir\'e graphene: Distinct observation of the superconducting gap and signatures of nodal superconductivity

Abstract

Understanding the nature of superconductivity in magic-angle graphene remains challenging. A key difficulty lies in discerning the different energy scales in this strongly interacting system, particularly the superconducting gap. Here, we report the first simultaneous tunneling spectroscopy and transport measurements of magic-angle graphene, providing a novel approach to probe the superconducting state. This approach allows us to identify two coexisting V-shaped tunneling gaps with different energy scales: a distinct low-energy superconducting gap that vanishes at the superconducting critical temperature and magnetic field, and a higher-energy pseudogap. The superconducting tunneling spectra display a linear gap-filling behavior with temperature and magnetic field and exhibit the Volovik effect, consistent with a nodal order parameter. Our work reveals the unconventional nature of the superconducting gap in magic-angle graphene and establishes an experimental framework for multidimensional investigation of tunable quantum materials.