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arXiv · 2610.19793

Orientation-Dependent Universality of Spin-Transport Fluctuations in Two-Dimensional Altermagnets

Yihan Zhang·Zheng Qin·Donghui Xu·Junjie Zeng·Zhen Ning·Rui Wang
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Abstract

Universal conductance fluctuations are conventionally organized by symmetry class, but crystalline anisotropy introduces additional structure in spin transport. Here we demonstrate orientation-dependent universal spin-transport fluctuations in disordered two-dimensional $d$-wave altermagnets without spin-orbit coupling. Rotating the altermagnetic orientation changes both longitudinal spin-conductance and transverse spin-Hall conductance fluctuations, while each conserved-spin sector remains in class AI. Altermagnetic orientation controls both the fluctuation amplitudes and the development of disorder-insensitive plateaus. These plateaus become flatter and less sensitive to the altermagnetic strength over the studied parameter ranges as the orientation approaches $45^\circ$, with representative fluctuation amplitudes of approximately $0.60e/(4π)$ for the longitudinal spin conductance and $0.40\,e/(4π)$ for the spin-Hall conductance. The longitudinal fluctuation amplitude correlates strongly with anisotropy of the clean-band Fermi-velocity tensor. Spin-sector covariances explain how the conserved channels combine into total fluctuations. Our results extend anisotropy-sensitive universal-fluctuation physics to conserved-spin altermagnetic transport and establish crystalline orientation as a control parameter within a fixed symmetry class.

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Yihan Zhang, Zheng Qin, Donghui Xu, Junjie Zeng, Zhen Ning, Rui Wang. 2026-10-14. Orientation-Dependent Universality of Spin-Transport Fluctuations in Two-Dimensional Altermagnets. https://arxiv.org/abs/2610.19793

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