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<p>Altermagnets, combining zero net magnetization with intrinsic spin splitting, demonstrate unique quantum phenomena crucial for spintronic applications. KV<sub>2</sub>Se<sub>2</sub>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, an 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<sub>2</sub>Se<sub>2</sub>O based on first-principles calculations. The spin canting driven by periodic spin modulation in the SDW phase reduces the magnetic symmetry of KV<sub>2</sub>Se<sub>2</sub>O. The resultant band degeneracy lifting and Fermi surface reconstruction induce the “inverse 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 a phase transition from transport signatures, providing a novel paradigm for altermagnet research.</p>

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Magnetic symmetry breaking driven “inverse magnetic breakdown” in a d-wave altermagnet KV2Se2O

  • 期刊论文

  • 发表日期：

    2026年2月3日

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  • Xu Yan,
  • Ziyin Song,
  • Juntao Song,
  • Zhong Fang,
  • Hongming Weng,
  • Quansheng Wu

摘要

Altermagnets, combining zero net magnetization with intrinsic spin splitting, demonstrate unique quantum phenomena crucial for spintronic applications. KV2Se2O 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, an 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 KV2Se2O based on first-principles calculations. The spin canting driven by periodic spin modulation in the SDW phase reduces the magnetic symmetry of KV2Se2O. The resultant band degeneracy lifting and Fermi surface reconstruction induce the “inverse 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 a phase transition from transport signatures, providing a novel paradigm for altermagnet research.