Emergent Surface Kondo Flat Band Driven by Competing Interactions in a Topological Ferromagnet
Abstract
A central goal of modern condensed matter physics is to uncover new quantum states of matter arising from the intertwined effects of strong electron correlations, magnetism, and band topology. Heavy-fermion phases, generated by Kondo interactions, represent one of the most remarkable manifestations of electronic correlations, and topological heavy-fermion states have been identified in several non-magnetic materials. Yet, the consequences of their competition with magnetic order have remained largely unexplored. Here, we reveal a new phenomenon: the spontaneous spatial separation of correlated quantum phases. By showing that magnetism can drive distinct strongly correlated electronic states to coexist in different regions of a single material, our work establishes a previously unknown mechanism for organizing quantum matter and opens a new direction in the study of correlated topological systems. Using \emph{bulk-sensitive} probes, we show that UAsS crystals are, in the bulk, metallic ferromagnets with only moderate correlation-driven band renormalizations. First-principles calculations reveal a topological electronic structure hosting both nodal lines and Weyl points, pointing to a rich underlying topology. Angle-resolved photoemission spectroscopy (ARPES) measurements are consistent with these predictions, resolving the nodal lines and Weyl crossings. In striking contrast, \emph{surface-sensitive} ARPES and scanning tunneling microscopy/spectroscopy (STM/STS) measurements reveal a pronounced flat band pinned at the Fermi level, accompanied by a sharp resonance -- hallmarks of an emergent, strongly correlated Kondo state not captured by first-principles calculations.
Related
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BibTeX
@misc{zaremba2026emergent,
title = {{Emergent Surface Kondo Flat Band Driven by Competing Interactions in a Topological Ferromagnet}},
author = {Nazar Zaremba and Susmita Changdar and Haojie Guo and Iñigo Robredo and Daniel Lozano-Gomez and Andreas Leithe-Jasper and Rui Lou and Yurii Prots and Mitja Krnel and Markus König and Konstantin Semeniuk and Berit H. Goodge and Yuri Grin and Andrii Kuibarov and Oleksandr Suvorov and Alexander Fedorov and Adam Pikul and Ivan Soldatov and Rudolf Schäfer and Bernd Büchner and Oksana Kvitnitskaya and Yurii Naidyuk and Louis Lamm and Meike Pfeiffer and Elena Hassinger and Matthias Vojta and Sergey Borisenko and Miguel M. Ugeda and Jeroen van den Brink and Eteri Svanidze and Maia G. Vergniory},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.20432},
eprint = {2609.20432},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.20432},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Emergent Surface Kondo Flat Band Driven by Competing Interactions in a Topological Ferromagnet
AU - Nazar Zaremba
AU - Susmita Changdar
AU - Haojie Guo
AU - Iñigo Robredo
AU - Daniel Lozano-Gomez
AU - Andreas Leithe-Jasper
AU - Rui Lou
AU - Yurii Prots
AU - Mitja Krnel
AU - Markus König
AU - Konstantin Semeniuk
AU - Berit H. Goodge
AU - Yuri Grin
AU - Andrii Kuibarov
AU - Oleksandr Suvorov
AU - Alexander Fedorov
AU - Adam Pikul
AU - Ivan Soldatov
AU - Rudolf Schäfer
AU - Bernd Büchner
AU - Oksana Kvitnitskaya
AU - Yurii Naidyuk
AU - Louis Lamm
AU - Meike Pfeiffer
AU - Elena Hassinger
AU - Matthias Vojta
AU - Sergey Borisenko
AU - Miguel M. Ugeda
AU - Jeroen van den Brink
AU - Eteri Svanidze
AU - Maia G. Vergniory
PY - 2026
DA - 2026/09/17
PB - arXiv
DO - 10.48550/arxiv.2609.20432
UR - https://arxiv.org/abs/2609.20432
AB - A central goal of modern condensed matter physics is to uncover new quantum states of matter arising from the intertwined effects of strong electron correlations, magnetism, and band topology. Heavy-fermion phases, generated by Kondo interactions, represent one of the most remarkable manifestations of electronic correlations, and topological heavy-fermion states have been identified in several non-magnetic materials. Yet, the consequences of their competition with magnetic order have remained largely unexplored. Here, we reveal a new phenomenon: the spontaneous spatial separation of correlated quantum phases. By showing that magnetism can drive distinct strongly correlated electronic states to coexist in different regions of a single material, our work establishes a previously unknown mechanism for organizing quantum matter and opens a new direction in the study of correlated topological systems. Using \emph{bulk-sensitive} probes, we show that UAsS crystals are, in the bulk, metallic ferromagnets with only moderate correlation-driven band renormalizations. First-principles calculations reveal a topological electronic structure hosting both nodal lines and Weyl points, pointing to a rich underlying topology. Angle-resolved photoemission spectroscopy (ARPES) measurements are consistent with these predictions, resolving the nodal lines and Weyl crossings. In striking contrast, \emph{surface-sensitive} ARPES and scanning tunneling microscopy/spectroscopy (STM/STS) measurements reveal a pronounced flat band pinned at the Fermi level, accompanied by a sharp resonance -- hallmarks of an emergent, strongly correlated Kondo state not captured by first-principles calculations.
ER -