Spectroscopic evidence for unconventional superconductivity in magic-angle twisted bilayer graphene

A question regarding the superconducting state in magic-angle twisted bilayer graphene (MATBG) remains whether the pairing mechanism is that of a conventional superconductor or the unconventional cases such like high-Tc superconductors, although various features of the superconducting phase have been reported in transport measurements. Tunneling measurement, otherwise, provides key information for understanding superconducting nature by studying Bogoliubov quasiparticle excitation spectra. In this talk, we report the unconventional spectroscopic features of the superconducting gap of the MATBG by using density-tuned scanning tunneling spectroscopy combined with Andreev reflection spectroscopy. We show that the tunnelling spectra below the transition temperature Tc are inconsistent with those of a conventional s-wave superconductor, but rather resemble those of a nodal superconductor with an anisotropic pairing mechanism.

Speaker: Myungchul Oh

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