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arXiv · 2607.13635

Transverse order and longitudinal fluctuations in a near-Ising spin supersolid

Mengze Zhu·V. Romerio·S. Raymond·N. Murai·S. Ohira-Kawamura·K. Yu. Povarov·S. A. Zvyagin·R. Sibille·A. Minelli·Z. Yan·S. Gvasaliya·A. Zheludev
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Abstract

We investigate the polarization of the ordered moments and low-energy spin fluctuations in the spin supersolid state of the S = 1/2 triangular-lattice easy-axis antiferromagnet K2Co(SeO3)2 using neutron scattering. The supersolid order develops through successive BKT transitions: the longitudinal order appears at higher temperature, while the transverse component associated with the Bose-Einstein condensate emerges only below a lower-temperature transition accompanied by a change in the interlayer correlations. At the lowest measured temperature, the transverse ordered moment reaches only 11% of the longitudinal component. Moreover, the low-energy spin fluctuations are found to be predominantly longitudinal in character. These results provide direct evidence that the supersolid ground state survives even in the near-Ising regime and exhibits longitudinal low-energy dynamics, imposing stringent constraints on microscopic theories of triangular-lattice XXZ antiferromagnets.

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Mengze Zhu, V. Romerio, S. Raymond, N. Murai, S. Ohira-Kawamura, K. Yu. Povarov, S. A. Zvyagin, R. Sibille, A. Minelli, Z. Yan, S. Gvasaliya, A. Zheludev. 2026-07-15. Transverse order and longitudinal fluctuations in a near-Ising spin supersolid. https://arxiv.org/abs/2607.13635

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