@article{8ceab08938fc4b8ea8964ca18052d75f,
title = "Visualizing broken symmetry and topological defects in a quantum Hall ferromagnet",
abstract = "The interaction between electrons in graphene under high magnetic fields drives the formation of a rich set of quantum Hall ferromagnetic (QHFM) phases with broken spin or valley symmetry. Visualizing atomic-scale electronic wave functions with scanning tunneling spectroscopy (STS), we resolved microscopic signatures of valley ordering in QHFM phases and spectral features of fractional quantum Hall phases of graphene. At charge neutrality, we observed a field-tuned continuous quantum phase transition from a valley-polarized state to an intervalley coherent state, with a Kekul{\'e} distortion of its electronic density. Mapping the valley texture extracted from STS measurements of the Kekul{\'e} phase, we could visualize valley skyrmion excitations localized near charged defects. Our techniques can be applied to examine valley-ordered phases and their topological excitations in a wide range of materials.",
author = "Xiaomeng Liu and Gelareh Farahi and Chiu, {Cheng Li} and Zlatko Papic and Kenji Watanabe and Takashi Taniguchi and Michael Zaletel and Ali Yazdani",
note = "Funding Information: Supported by NSF-DMR-1904442 and ONR-N00014-21-1-2592; Gordon and Betty Moore Foundation EPiQS initiative grant GBMF9469; NSF-MRSEC through the Princeton Center for Complex Materials NSF-DMR-2011750; DOE-BES grant DE-FG02-07ER46419; the Princeton Catalysis Initiative; the Elemental Strategy Initiative, Japan, grant JPMXP0112101001, JSPS KAKENHI grant JP20H00354, and CREST (JPMJCR15F3), JST (K.W. and T.T.); and the Army Research Office through the MURI program (grant W911NF-17-1-0323) (M.P.Z.). A.Y. acknowledges the hospitality of the Aspen Center for Physics, which is supported by NSF grant PHY-1607611, and Trinity College, where his stay was supported by a QuantEmX grant from ICAM and the Gordon and Betty Moore Foundation through grant GBMF9616. Publisher Copyright: Copyright {\textcopyright} 2022 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works",
year = "2022",
month = jan,
day = "21",
doi = "10.1126/science.abm3770",
language = "English (US)",
volume = "375",
pages = "321--326",
journal = "Science",
issn = "0036-8075",
publisher = "American Association for the Advancement of Science",
number = "6578",
}