Evidence for topological flat band magnetism in Co3Sn2S2
Abstract
Correlations and topology are central pillars in the study of emergent electronic phases. Topological flat bands near the Fermi level unite these concepts, providing a route towards correlated topological phenomena and unconventional magnetism. Despite theoretical predictions, momentum-resolved observation of a topological flat band at the Fermi level has remained elusive. Using angle resolved photoemission spectroscopy, we observe a flat band at the Fermi level within the topologically non-trivial electronic structure of the magnetic kagome Weyl semimetal Co3Sn2S2. We further uncover a strong temperature dependence in which the flat band shifts across the Fermi level, accompanied by a reconstruction of the Fermi surface. Strikingly, this evolution occurs on the same temperature scale as previously reported anomalies in the magnetic response. Together, these results provide evidence for topological flat band magnetism in Co3Sn2S2, establishing a microscopic setting in which topology, electronic correlations, and magnetism become intertwined.
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BibTeX
@misc{forslund2026evidence,
title = {{Evidence for topological flat band magnetism in Co$_3$Sn$_2$S$_2$}},
author = {Ola Kenji Forslund and Andrzej Ptok and Chun Lin and Aksel Kobialka and Wan Yu Chen and Ugne Miniotaite and Martin Månsson and Yasmine Sassa and Timur Kim and Cephise Cacho and Jian Rui Soh and Chin Shen Ong and Vladislav Borisov and Olle Eriksson and Johan Chang},
howpublished = {arXiv},
year = {2026},
month = nov,
doi = {10.48550/arxiv.2611.00310},
eprint = {2611.00310},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2611.00310},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Evidence for topological flat band magnetism in Co_3Sn_2S_2
AU - Ola Kenji Forslund
AU - Andrzej Ptok
AU - Chun Lin
AU - Aksel Kobialka
AU - Wan Yu Chen
AU - Ugne Miniotaite
AU - Martin Månsson
AU - Yasmine Sassa
AU - Timur Kim
AU - Cephise Cacho
AU - Jian Rui Soh
AU - Chin Shen Ong
AU - Vladislav Borisov
AU - Olle Eriksson
AU - Johan Chang
PY - 2026
DA - 2026/11/01
PB - arXiv
DO - 10.48550/arxiv.2611.00310
UR - https://arxiv.org/abs/2611.00310
AB - Correlations and topology are central pillars in the study of emergent electronic phases. Topological flat bands near the Fermi level unite these concepts, providing a route towards correlated topological phenomena and unconventional magnetism. Despite theoretical predictions, momentum-resolved observation of a topological flat band at the Fermi level has remained elusive. Using angle resolved photoemission spectroscopy, we observe a flat band at the Fermi level within the topologically non-trivial electronic structure of the magnetic kagome Weyl semimetal Co_3Sn_2S_2. We further uncover a strong temperature dependence in which the flat band shifts across the Fermi level, accompanied by a reconstruction of the Fermi surface. Strikingly, this evolution occurs on the same temperature scale as previously reported anomalies in the magnetic response. Together, these results provide evidence for topological flat band magnetism in Co_3Sn_2S_2, establishing a microscopic setting in which topology, electronic correlations, and magnetism become intertwined.
ER -