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Interaction-driven flat band and charge order in Fe5GeTe2
Qiang Gao1, Gabriele Berruto1, Khanh Duy Nguyen1
1Pritzker School of Molecular Engineering, The University of Chicago, Chicago, Illinois 60637, USA.
Science Advances
|August 7, 2026
Summary
Researchers discovered interaction-driven flat bands and charge order in Fe5GeTe2, a van der Waals magnet. This finding suggests a new way to achieve electronic ordering through strong correlations, potentially enabling novel quantum phenomena.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Quantum Materials
Background:
- Flat electronic bands are crucial for emergent phenomena like superconductivity and charge orders.
- Current methods often rely on geometric constraints in materials like twisted or kagome lattices.
- Achieving purely electronic-interaction-driven flat bands is challenging due to the need for strong interactions, which can lead to incoherent states.
Purpose of the Study:
- To investigate the concurrent formation of interaction-driven flat bands and electronic ordering in a van der Waals magnet.
- To explore the role of strong electronic correlations in material properties.
- To establish a new paradigm for promoting large-scale electronic ordering.
Main Methods:
- High-resolution angle-resolved photoemission spectroscopy (ARPES).
- Analysis of band structure and spectral weight.
- Temperature-dependent measurements.
Main Results:
- Concurrent formation of an interaction-driven flat band at the Fermi level and a charge order in Fe5GeTe2.
- Charge order manifested by band folding, driven by flat band nesting.
- Flat band observed throughout the Brillouin zone, with temperature-dependent spectral weight suggesting a coherent Fermi liquid state.
Conclusions:
- An interaction-driven flat band can promote large-scale electronic ordering.
- Strong correlations can lead to coherent Fermi liquid behavior.
- Fe5GeTe2 serves as a model system for studying interaction-driven phenomena.
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