Visualizing broken symmetry and topological defects in a quantum Hall ferromagnet

Xiaomeng Liu, Gelareh Farahi, Cheng Li Chiu, Zlatko Papic, Kenji Watanabe, Takashi Taniguchi, Michael P. Zaletel, Ali Yazdani

Research output: Contribution to journalArticlepeer-review

50 Scopus citations


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 Kekulé distortion of its electronic density. Mapping the valley texture extracted from STS measurements of the Kekulé 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.

Original languageEnglish (US)
Pages (from-to)321-326
Number of pages6
Issue number6578
StatePublished - Jan 21 2022

All Science Journal Classification (ASJC) codes

  • General


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