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<p>Circular dichroism originates from symmetry breaking in a material structure and leads to differential absorption of left-handed and right-handed circularly polarized light. However, circular dichroism in most materials is inherently weak and spectrally narrow, especially in the mid-to-far infrared. Here we uncover giant infrared circular dichroism in the magnetic-field-forced Weyl semimetal Mn(Bi,Sb)<sub>2</sub>Te<sub>4</sub> driven by extreme particle–hole symmetry breaking. Helicity-resolved magneto-infrared spectroscopy reveals circular dichroism exceeding 3,000 mdeg (~130 mdeg nm<sup>−1</sup>) with an above-degree response extending over the 6–13 μm spectral range. The optical resonances are enhanced by a strong band nesting effect intrinsic to the Landau levels of type-II Weyl dispersion. A symmetry-based k·p model reproduces these magneto-infrared responses and demonstrates that magnetization-induced asymmetric spin–orbit coupling generates particle–hole symmetry breaking, which suppresses spin-up, parity-even wavefunction components in the valence Landau band and thereby produces pronounced optical helicity-selectivity. Our findings establish particle–hole symmetry breaking as an effective route towards helicity-resolved optical control in quantum materials.</p>

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Giant and broadband circular dichroism from particle–hole symmetry breaking in Weyl semimetals

  • 期刊论文

  • 发表日期：

    2026年6月24日

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  • Xiangyu Jiang,
  • Zeping Shi,
  • Yuhan Du,
  • Haonan Chen,
  • Jiayu Wang,
  • Wenbin Wu,
  • Guangyi Wang,
  • Congming Hao,
  • Mingfan Yao,
  • Mingsen Zhou,
  • Xin Chen,
  • Chenyao Xu,
  • Zhongbo Yan,
  • Cheng Zhang,
  • Hai-Zhou Lu,
  • Junhao Chu,
  • Xiang Yuan

摘要

Circular dichroism originates from symmetry breaking in a material structure and leads to differential absorption of left-handed and right-handed circularly polarized light. However, circular dichroism in most materials is inherently weak and spectrally narrow, especially in the mid-to-far infrared. Here we uncover giant infrared circular dichroism in the magnetic-field-forced Weyl semimetal Mn(Bi,Sb)2Te4 driven by extreme particle–hole symmetry breaking. Helicity-resolved magneto-infrared spectroscopy reveals circular dichroism exceeding 3,000 mdeg (~130 mdeg nm−1) with an above-degree response extending over the 6–13 μm spectral range. The optical resonances are enhanced by a strong band nesting effect intrinsic to the Landau levels of type-II Weyl dispersion. A symmetry-based k·p model reproduces these magneto-infrared responses and demonstrates that magnetization-induced asymmetric spin–orbit coupling generates particle–hole symmetry breaking, which suppresses spin-up, parity-even wavefunction components in the valence Landau band and thereby produces pronounced optical helicity-selectivity. Our findings establish particle–hole symmetry breaking as an effective route towards helicity-resolved optical control in quantum materials.