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arXiv · 2510.14593

Interplay of ferromagnetism, nematicity and Fermi surface nesting in kagome flat band

Yuman He·Wentao Jiang·Siqi Wu·Xuzhe Ying·Berthold Jack·Xi Dai·Hoi Chun Po
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Abstract

Recent experiment on Fe-doped CoSn has uncovered a series of correlated phases upon hole doping of the kagome flat bands. Among the phases observed, a nematic phase with a six- to two-fold rotation symmetry breaking is found to prevail over a wide doping and temperature range. Motivated by these observations, we investigate the interaction-driven phases realized in a kagome model with partially filled, weakly dispersing flat bands. Density-density interactions up to second-nearest neighbors are considered. We identify a close competition between ferromagnetic and nematic phases in our self-consistent Hartree-Fock calculations: while on-site interaction favors ferromagnetism, the sizable inter-sublattice interactions stabilize nematicity over a wide doping window. Competition from translational-symmetry-breaking phases is also considered. Overall, our results show that nematicity is a generic outcome of partially filled kagome flat bands and establish a minimal framework for understanding correlated flat-band phases.

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Yuman He, Wentao Jiang, Siqi Wu, Xuzhe Ying, Berthold Jack, Xi Dai, Hoi Chun Po. 2025-10-16. Interplay of ferromagnetism, nematicity and Fermi surface nesting in kagome flat band. https://arxiv.org/abs/2510.14593

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