Progress in quantum transport study of magic-angle twisted bilayer/bilayer graphene

Magic-angle twisted bilayer/bilayer graphene (TBBG) has shown various kinds of correlated electronic phases including superconductivity, ferromagnetism, Mott insulator [1, 2]. First, we discuss our dry transfer technique for making atomically clean TBBG with so-called tear-and-stack process. In our experiment, we measured the electron-electron interaction induced Mott insulating state at half fillings. We also observed the signature of superconducting phase near Mott insulating phase, and investigated by measuring temperature dependence and magnetic field dependence of current-voltage characteristics. As twist angle uniformity is crucial to form a macroscopic superconducting phase [3], we discuss our efforts and progress in realizing more homogeneous twist angle in TBBG devices.

REFERENCES:
[1] Cao, Y., et al. (2018). "Unconventional superconductivity in magic-angle graphene superlattices." Nature 556(7699): 43-50.
[2] Xiaomeng Liu, et al. (2019). "Spin-polarized Correlated Insulator and Superconductor in Twisted Double Bilayer Graphene." arXiv:1903.08130
[3] Xiaobo Lu, et al. (2019). “Superconductors, Orbital Magnets, and Correlated States in Magic Angle Bilayer Graphene.” arXiv:1903.06515