[DSRP Evidence](https://dsrpevidence.org/)

# Interaction-driven flat band and charge order in Fe5GeTe2

Gao et al., 2026, Science Advances — Materials Science

Patterns: [Systems](https://dsrpevidence.org/pattern/systems), [Relationships](https://dsrpevidence.org/pattern/relationships)

## In short

The result is a whole-system emergent behavior — large groups of electrons collectively slowed while remaining quantum-coherent, unlike any single electron — that is itself coupled to a second subsystem (magnetic order), so the finding needs both the part-whole emergence and the cross-subsystem relationship to be stated fully.

## What they found (results)

Time- and angle-resolved spectroscopy on the van der Waals magnet Fe5GeTe2 revealed an interaction-driven flat electronic band and charge-ordered state in which large groups of electrons move collectively at greatly reduced effective velocity, with this charge order coupled to the material's magnetic ordering up to about 100 K.

## Abstract

Flat electronic bands enable fascinating emergent phenomena such as superconductivity and charge orders. A prevailing approach to realizing flat bands is to engineer lattice geometric constraints in twisted or kagome-like materials. An alternative approach is to utilize purely electronic-interaction-driven flat bands, yet a fundamental challenge is that extreme flatness requires ultrastrong interaction strength, which often leads to incoherent states. Here we demonstrate the concurrent formation of an interaction-driven flat band at the Fermi level and a 3 × 3 R 30 ° charge order in a van der Waals magnet Fe 5 GeTe 2 using high-resolution angle-resolved photoemission spectroscopy. This charge order is manifested by band folding within 30 meV below the Fermi level, with its nesting driven by flat bands. The presence of this flat band throughout the Brillouin zone and the logarithmic temperature dependence of its spectral weight suggest a phenomenological Kondo-like, coherent Fermi liquid emerging from strong correlations. Our work establishes a paradigm where an interaction-driven flat band promotes large-scale electronic ordering.

These researchers were not testing DSRP. The finding is theirs; the correspondence to DSRP is drawn by this site.

[Source](https://doi.org/10.1126/sciadv.aeg5930)