Imaging the many-body wavefunctions in magic-angle graphene
ORAL
Abstract
Magic-angle twisted bilayer graphene (MATBG) hosts a set of flat electronic bands that produce a wide variety of correlated ground states including superconductors, correlated insulators, and magnetic topological phases. Our understanding of these phases has thus far been hampered by the lack of microscopic, atomic-scale information on them. In this talk, I will discuss how we use high-resolution scanning tunneling microscopy (STM) measurements to study the wavefunctions of these correlated phases. STM images reveal distinct symmetry-breaking patterns with a sqrt(3) x sqrt(3) superperiodicity on the graphene atomic lattice. To understand these patterns, we develop a symmetry-based analysis to visualize the images in terms of a set of complex-valued order parameters. At the correlated insulators at fillings ±2 electrons per moiré unit cell, comparison with theoretical candidates reveals a close match with the proposed incommensurate Kekulé spiral order in samples with typical values of interlayer strain, while in ultralow-strain samples, our data have local symmetries resembling the time-reversal symmetric intervalley coherent phase. These symmetry-based techniques can be further applied to other phases in MATBG, graphene systems, and potentially other material systems.
*This work was primarily supported by the Gordon and Betty Moore Foundation's EPiQS initiative grants GBMF9469 and DOE-BES grant DE-FG02-07ER46419 to A.Y. Other support for the experimental work was provided by NSF-MRSEC through the Princeton Center for Complex Materials NSF-DMR- 2011750, NSF-DMR-1904442, ARO MURI (W911NF-21-2-0147) and ONR N00012-21-1-2592. K.W. and T.T. acknowledge support from the Elemental Strategy Initiative conducted by the MEXT, Japan, grant JPMXP0112101001, JSPS KAKENHI grants 19H05790 and JP20H00354.
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Publication:Nuckolls, K.P., Lee, R.L., Oh, M. et al. Quantum textures of the many-body wavefunctions in magic-angle graphene. Nature 620, 525–532 (2023). https://doi.org/10.1038/s41586-023-06226-x
Presenters
Ryan L Lee
Princeton University
Authors
Ryan L Lee
Princeton University
Kevin P Nuckolls
Massachusetts Institute of Technology
Myungchul Oh
Princeton University
Pohang University of Science and Technology
Dillon Wong
Princeton University
Tomohiro Soejima
Harvard University; IBM Quantum, Almaden Research Center
Harvard University
Jung Pyo Hong
Princeton University
Dumitru Calugaru
Princeton University
Jonah Herzog-Arbeitman
Princeton University
Andrei B Bernevig
Princeton University
Kenji Watanabe
National Institute for Materials Science
NIMS
Research Center for Electronic and Optical Materials, National Institute for Materials Science
Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
National Institute for Material Science
Takashi Taniguchi
Kyoto Univ
National Institute for Materials Science
Research Center for Materials Nanoarchitectonics
Research Center for Materials Nanoarchitectonics, National Institute for Materials Science
National Institute for Materials Sciences
NIMS
International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
National Institute for Material Science
International Center for Materials Nanoarchitectonics, NIMS, Japan
International Center for Materials Nanoarchitectonics, Tsukuba
National Institue for Materials Science
Kyoto University
National Institute of Materials Science
International Center for Materials Nanoarchitectonics and National Institute for Materials Science
