Tunable quantum interferometer for correlated moiré electrons

• Published in: Nature communications 2024-01, Vol.15 (1), p.390-390, Article 390
• Main Authors: Iwakiri, Shuichi, Mestre-Torà, Alexandra, Portolés, Elías, Visscher, Marieke, Perego, Marta, Zheng, Giulia, Taniguchi, Takashi, Watanabe, Kenji, Sigrist, Manfred, Ihn, Thomas, Ensslin, Klaus
• Format: Article
• Language: English
• Subjects: 639/766/1130/1064; 639/925/918/1052; Bilayers; Coherence length; Correlation; Electrons; Graphene; Humanities and Social Sciences; Magnetic fields; multidisciplinary; Oscillations; Parks; Parks & recreation areas; Phase diagrams; Science; Science (multidisciplinary); Superconductivity
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-023-44671-4

Magic-angle twisted bilayer graphene can host a variety of gate-tunable correlated states – including superconducting and correlated insulator states. Recently, junction-based superconducting moiré devices have been introduced, enabling the study of the charge, spin and orbital nature of superconductivity, as well as the coherence of moiré electrons in magic-angle twisted bilayer graphene. Complementary fundamental coherence effects—in particular, the Little–Parks effect in a superconducting ring and the Aharonov–Bohm effect in a normally conducting ring – have not yet been reported in moiré devices. Here, we observe both phenomena in a single gate-defined ring device, where we can embed a superconducting or normally conducting ring in a correlated or band insulator. The Little–Parks effect is seen in the superconducting phase diagram as a function of density and magnetic field, confirming the effective charge of 2 e . We also find that the coherence length of conducting moiré electrons exceeds several microns at 50 mK. In addition, we identify a regime characterized by h / e -periodic oscillations but with superconductor-like nonlinear transport. Gate-defined superconducting moiré devices offer high tunability for probing the nature of superconducting and correlated insulating states. Here, the authors report the Little–Parks and Aharonov–Bohm effects in a single gate-defined magic-angle twisted bilayer graphene device.