Observation of strain-locked in-plane spin orders in a 2D XY antiferromagnet

ORAL

Abstract

It is believed that no long-range magnetic order exists in a 2D magnet with the XY anisotropy under Mermin–Wagner theorem. Surprisingly, we directly observe the long-range antiferromagnetic (AFM) N\'eel orders in an XY magnet MnPSe$_3$ down to monolayer by optical second-harmonic generation (SHG) microscopy. We further demonstrate the directions of the in-plane spins are decoupled to the crystalline axes and actually locked by the external strains. A simple Ginzburg–Landau theory is applied to explain our observation, where an inevitable tiny strain in the real world would drive the system from XY Universality class to Ising Universality class and help stabilize the long-range orders. Our work also demonstrate the SHG microscopy as a powerful tool to imaging AFM spin structures in 2D magnets.

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Publication: [1] Ni, Z., Haglund, A.V., Wang, H. et al. Imaging the Néel vector switching in the monolayer antiferromagnet MnPSe3 with strain-controlled Ising order. Nat. Nanotechnol. 16, 782–787 (2021).
[2] Ni,Z., Zhang, H., Hopper, D., Direct imaging of antiferromagnetic domains and anomalous layer-dependent mirror symmetry breaking in atomically thin MnPS3. arXiv:2110.02349.

Presenters

  • Zhuoliang Ni

    • University of Pennsylvania

Authors

  • Zhuoliang Ni

    • University of Pennsylvania

  • Amanda V Haglund

    • University of Tennesseea
    • University of Tennessee
    • Department of Materials Science and Engineering, The University of Tennessee

  • Hua Wang

    • Texas A&M University

  • Bing Xu

    • Department of Physics and Fribourg Center for Nanomaterials,, University of Fribourg
    • University of Fribourg

  • Christian Bernhard

    • University of Fribourg

  • David G Mandrus

    • University of Tennessee
    • Department of Materials Science and Engineering, University of Tennessee, Knoxville, TN, 37916, USA

  • Xiaofeng Qian

    • Texas A&M University

  • Eugene J Mele

    • University of Pennsylvania

  • Charles L Kane

    • University of Pennsylvania

  • Liang Wu

    • University of Pennsylvania