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arXiv · 2610.34439

Theory of the $1/9$ Magnetization Plateau of the Spin-$1/2$ Kagome Heisenberg Antiferromagnet

Pratyay Ghosh·Frédéric Mila
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Abstract

We investigate the $1/9$ magnetization plateau of the spin-$1/2$ kagome Heisenberg antiferromagnet using infinite projected entangled-pair states and identify a spin-density-wave state with a $27$-site unit cell and a lower variational energy than previous approaches. In contrast to higher-magnetization plateaus, which are well described by localized magnons on nonoverlapping hexagons and preserve a sixfold rotational symmetry, the $1/9$ plateau only keeps a threefold rotational symmmetry and consists of a tiling by three types of $9$-site clusters related by $\pm2π/3$ rotations. These conclusions are supported by a complementary cluster mean-field theory which correctly preserves the symmetry of the higher plateaus but leads to the same spontaneous symmetry breaking for the $1/9$ plateau with a qualitatively similar pattern of nine different local magnetizations.

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Pratyay Ghosh, Frédéric Mila. 2026-10-25. Theory of the $1/9$ Magnetization Plateau of the Spin-$1/2$ Kagome Heisenberg Antiferromagnet. https://arxiv.org/abs/2610.34439

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