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arXiv · 2505.00074

SDW driven "magnetic breakdown" in a d-wave altermagnet KV$_2$Se$_2$O

Xu Yan·Ziyin Song·Juntao Song·Zhong Fang·Hongming Weng·Quansheng Wu
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Abstract

Altermagnets, combining zero net magnetization with intrinsic spin splitting, demonstrate unique quantum phenomena crucial for spintronic applications. KV$_2$Se$_2$O is proven to be a d-wave altermagnet with phase transition from a checkerboard-type (C-type) antiferromagnetic (AFM) state to a spin density wave (SDW) state as the temperature decreases. After phase transition, the apparent paradox emerges where angle-resolved photoemission spectroscopy (ARPES) reveals negligible Fermi surface modifications, while physical property measurement system (PPMS) measurements uncover substantial changes in transport properties. Our study explores the microscopic mechanisms governing phase-dependent transport properties of KV$_2$Se$_2$O base on first-principles calculations. The spin canting driven by periodic spin modulation in the SDW phase reduces the magnetic symmetry of KV$_2$Se$_2$O. The resultant band degeneracy lifting and Fermi surface reconstruction induce the ``magnetic breakdown" phenomenon, which alters carrier trajectories, modifies carrier concentration, strengthens electron-hole compensation, and ultimately accounts for the contrasting magnetic-field-dependent Hall resistivity relative to the C-type AFM state. Our work proposes an innovative method for identifying the electronic structure evolution across phase transitions from transport signatures, providing a novel paradigm for altermagnets research.

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Xu Yan, Ziyin Song, Juntao Song, Zhong Fang, Hongming Weng, Quansheng Wu. 2025-04-30. SDW driven "magnetic breakdown" in a d-wave altermagnet KV$_2$Se$_2$O. https://doi.org/10.1007/s11433-025-2881-5

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