Related Experiment Video
Updated: Oct 11, 2025
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Visualizing Uniaxial-strain Manipulation of Antiferromagnetic Domains in Fe1+YTe Using a Spin-polarized Scanning Tunneling Microscope
Published on: March 24, 2019
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Visualizing broken symmetry and topological defects in a quantum Hall ferromagnet
Xiaomeng Liu1, Gelareh Farahi1, Cheng-Li Chiu1
1Joseph Henry Laboratories and Department of Physics, Princeton University, Princeton, NJ 08544, USA.
Science (New York, N.Y.)
|December 2, 2021
Summary
Researchers visualized atomic-scale electronic wave functions in graphene's quantum Hall ferromagnetic phases using scanning tunneling spectroscopy. They observed valley ordering and a continuous phase transition, revealing valley skyrmion excitations.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Quantum Mechanics
Background:
- Graphene exhibits complex quantum Hall ferromagnetic (QHFM) phases under high magnetic fields.
- These phases involve broken spin or valley symmetry, influencing electronic properties.
- Understanding these phases requires visualizing atomic-scale electronic wave functions.
Purpose of the Study:
- To resolve microscopic signatures of valley ordering in QHFM phases using scanning tunneling spectroscopy (STS).
- To investigate spectral features of fractional quantum Hall phases in graphene.
- To map valley texture and visualize topological excitations like valley skyrmions.
Main Methods:
- Utilized scanning tunneling spectroscopy (STS) to visualize atomic-scale electronic wave functions.
- Applied high magnetic fields to induce and study QHFM phases in graphene.
- Analyzed spectral features and mapped valley texture from STS measurements.
Main Results:
- Resolved microscopic signatures of valley ordering in QHFM phases.
- Observed a field-tuned continuous quantum phase transition at charge neutrality.
- Identified an intervalley coherent state with Kekulé distortion and visualized valley skyrmions near defects.
Conclusions:
- STS is effective for resolving valley ordering and topological excitations in graphene's QHFM phases.
- The study reveals a novel continuous phase transition and valley skyrmion behavior.
- The techniques are applicable to studying valley-ordered phases in diverse materials.
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