Regensburg 2022 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 2: Nanotubes, Nanoribbons and Graphene
TT 2.10: Vortrag
Montag, 5. September 2022, 12:00–12:15, H22
Mapping electrostatically tunable bands in twisted double bilayer graphene in magnetic fields — •Yulia Maximenko1,2, Marlou Slot1,3, Sungmin Kim1,2, Daniel Walkup1, Evgheni Strelcov1, En-Min Shih1,3, Dilek Yildiz1,2, Steven Blankenship1, Kenji Watanabe4, Takashi Taniguchi4, Yafis Barlas5, Paul Haney1, Nikolai Zhitenev1, Fereshte Ghahari6, and Joseph Stroscio1 — 1NIST MD USA — 2U of Maryland USA — 3Georgetown U DC USA — 4NIMS Tsukuba Japan — 5U of Nevada-Reno NV USA — 6George Mason U VA USA
After the first demonstration of superconductivity in magic-angle twisted bilayer graphene (MATBG), 2D moiré superlattices proved to be valuable systems for band engineering and studying correlated quantum phases. An imposed periodic potential can drive a crystal into a flat-band phase facilitating strong electron-electron interactions. In MATBG, flat bands appear only at a few precise values of the twist angle. In contrast, small-angle twisted double bilayer graphene (TDBG) can be tuned in and out of the correlated regime using electrostatic fields in a continuous range of twist angles. Local probe studies are key to avoid the common complication of angle disorder. Here we employ scanning tunneling microscopy and electrostatic gating to study TDBG with atomic spatial and high energy resolution in magnetic fields up to 15 T. We observe Landau quantization and map out the TDBG band structure in response to the applied electric field. We use theoretical modeling of the effects of displacement fields, Berry curvature, and magnetic fields to support our experimental findings.