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arXiv · 2510.03322

Proper Theory of Magnon Orbital Angular Momentum at Equilibrium

Junyu Tang·Ran Cheng
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Abstract

The orbital motion of chargeless bosons, unlike that of electrons, does not generate a magnetic moment and thus cannot directly interact with magnetic fields. To formulate the orbital angular momentum (OAM) of magnons, we first identify its proper conjugate variable by considering the Aharonov-Casher effect, which gives rise to a virtual perturbation to the equilibrium state, allowing us to calculate the magnon OAM as a virtual response to an infinitesimal electric field divergence. At finite temperatures, both self-rotation and topological contributions to the magnon OAM are explicitly derived, analogous to their electronic counterpart but with the correct bosonic statistics. In a two-dimensional honeycomb lattice, we show that the Dzyaloshinskii-Moriya interaction induces a large magnon OAM in both the ferromagnetic and antiferromagnetic phases. Our formalism can be generalized to other chargeless bosons with intrinsic spin.

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Junyu Tang, Ran Cheng. 2025-10-01. Proper Theory of Magnon Orbital Angular Momentum at Equilibrium. https://doi.org/10.1103/fgt6-bhmq

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