Large Nonreciprocal Charge Transport in Superconducting Gallium-Intercalated Graphene

Nonreciprocal charge transport and the superconducting diode effect have been observed in several superconducting materials. Both phenomena have been closely linked to the strong spin-orbit coupling in these superconducting materials. In this work, we employed confinement heteroepitaxy to synthesize a wafer-scale gallium (Ga)-intercalated epitaxial bilayer graphene on SiC, where the spin-orbit coupling is expected to be weak. By performing second harmonic measurements, we observed large nonreciprocal charge transport with a coefficient up to ~3000 ×10^-3 T^-1A^-1m. This observation is consistent with our recent work on Pauli-limit violation, which provides evidence for Ising-type superconductivity in Ga-intercalated graphene on SiC. Both phenomena are attributed to large Ising-type spin splitting induced by band hybridization between the Ga films and the SiC substrate. This work will advance our understanding of the formation of the Ising-type superconductivity in Ga-intercalated graphene/SiC and motivate more studies on nonreciprocal charge transport in artificially engineered materials.