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<p>Itinerant antiferromagnets with broken time-reversal symmetry have recently attracted attention, since their spin-split bands enable large magnetotransport responses comparable to ferromagnets despite the negligible spontaneous magnetisation. When the inversion symmetry is further broken by the antiferromagnetic order, the emerging odd-parity multipole order renders the bands spin-degenerate but asymmetric in the momentum space. For such parity-time-symmetric antiferromagnets, it has been predicted that electronic nematicity is induced by current, allowing unconventional nonlinear transport phenomena. However, their experimental evidence has been lacking. Here, we report two-fold nonreciprocal angular magnetoresistance in the tetragonal layered Dirac material SrMnBi<sub>2</sub> with parity-time-symmetric antiferromagnetic order in its Mn-Bi layers. By quantitatively modelling the angular and field dependencies using a phenomenological framework, we reveal that the observed nonreciprocal interlayer resistivity arises from the current-induced breaking of four-fold rotoinversion symmetry of the Dirac valleys in the Bi square net adjacent to the Mn-Bi layer. Furthermore, we demonstrate the alignment of parity-time-symmetric antiferromagnetic domains via current-field cooling, achieving electric-magnetic control of the <i>f</i>-wave polarity in momentum space. The observed switchable nonreciprocal transport associated with current-tuneable valley nematicity paves the way for novel antiferromagnetic spintronic and valleytronic applications.</p>

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Transport evidence of current-induced nematic Dirac valleys in a parity-time-symmetric antiferromagnet

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年1月7日

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  • Hideaki Sakai,
  • Yuya Miyamoto,
  • Motoi Kimata,
  • Hikaru Watanabe,
  • Yoichi Yanase,
  • Masayuki Ochi,
  • Masaki Kondo,
  • Hiroshi Murakawa,
  • Noriaki Hanasaki

摘要

Itinerant antiferromagnets with broken time-reversal symmetry have recently attracted attention, since their spin-split bands enable large magnetotransport responses comparable to ferromagnets despite the negligible spontaneous magnetisation. When the inversion symmetry is further broken by the antiferromagnetic order, the emerging odd-parity multipole order renders the bands spin-degenerate but asymmetric in the momentum space. For such parity-time-symmetric antiferromagnets, it has been predicted that electronic nematicity is induced by current, allowing unconventional nonlinear transport phenomena. However, their experimental evidence has been lacking. Here, we report two-fold nonreciprocal angular magnetoresistance in the tetragonal layered Dirac material SrMnBi2 with parity-time-symmetric antiferromagnetic order in its Mn-Bi layers. By quantitatively modelling the angular and field dependencies using a phenomenological framework, we reveal that the observed nonreciprocal interlayer resistivity arises from the current-induced breaking of four-fold rotoinversion symmetry of the Dirac valleys in the Bi square net adjacent to the Mn-Bi layer. Furthermore, we demonstrate the alignment of parity-time-symmetric antiferromagnetic domains via current-field cooling, achieving electric-magnetic control of the f-wave polarity in momentum space. The observed switchable nonreciprocal transport associated with current-tuneable valley nematicity paves the way for novel antiferromagnetic spintronic and valleytronic applications.