Topological metal-insulator transition within the ferromagnetic state
- Ola Kenji Forslund
- Chin Shen Ong
- Moritz M. Hirschmann
- Nicolas Gauthier
- Hiroshi Uchiyama
- Christian Tzschaschel
- Daniel G. Mazzone
- Romain Sibille
- Antonio M. dos Santos
- Masafumi Horio
- Elisabetta Nocerino
- Nami Matsubara
- Deepak John Mukkattukavil
- Konstantinos Papadopoulos
- Kazuya Kamazawa
- Kazuhiko Ikeuchi
- Hidenori Takagi
- Masahiko Isobe
- Jun Sugiyama
- Johan Chang
- Yasmine Sassa
- Olle Eriksson
- Martin Månsson
2026-02-27
A major challenge in condensed matter physics is integrating topological phenomena with correlated electron physics to leverage both types of states for next-generation quantum devices. Metal-insulator transitions are central to bridging these two domains while simultaneously serving as on-off switches for electronic states. Here, we demonstrate how the prototypical material of K 2 Cr 8 O 16 undergoes a ferromagnetic metal-insulator transition accompanied by a change in band topology. Through inelastic x-ray and neutron scattering experiments combined with first-principles theoretical calculations, we show that this transition is not driven by a Peierls mechanism, given the lack of phonon softening. Instead, we establish the transition as a topological metal-insulator transition within the ferromagnetic phase with potential axionic properties, where electron correlations play a key role in stabilizing the insulating state. These results reveal how a metal-insulator transition provides a pathway through which magnetism, topology, and electronic correlations interact.