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arXiv · 2603.23145

Impurity quadrupole moments as local probes of flux sectors in the Kitaev spin liquid

Masahiro O. Takahashi·Wen-Han Kao·Satoshi Fujimoto·Natalia B. Perkins
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Abstract

Emergent fluxes play a central role in the low-energy properties of quantum spin liquids (QSLs), where they encode the underlying gauge structure and fractionalization of spins. Here, we show that the quadrupole moment of magnetic impurities provides a direct probe of these flux configurations in QSLs and can be measured by local tunneling spectroscopy. Employing the SO(6) Majorana representation for spin-3/2 impurity operators in the isotropic Kitaev spin liquid together with a self-consistent mean-field approximation for impurity-related terms, we show that the ground-state flux sector can be identified by discontinuous jumps of the impurity quadrupole moment at the flux sector transition points. We also demonstrate that the quadrupole correlations between impurities under a magnetic field exhibit exponential decay, with decay rates that depend sensitively on the flux sector. Furthermore, we discuss the stability of pi fluxes bound to impurities with respect to model parameters and internal flux configurations, and relate our findings to Lieb's conjecture on flux configurations. These results establish the quadrupole moments of magnetic impurities as a sensitive tool to study fractionalized excitations and flux physics in Kitaev magnets.

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Masahiro O. Takahashi, Wen-Han Kao, Satoshi Fujimoto, Natalia B. Perkins. 2026-03-24. Impurity quadrupole moments as local probes of flux sectors in the Kitaev spin liquid. https://arxiv.org/abs/2603.23145

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