A type-II multiferroic in two dimensions
ORAL · Invited
Abstract
Multiferroic materials have garnered wide interest for their exceptional static and dynamical magnetoelectric properties [1]. In particular, type-II multiferroics exhibit an inversion-symmetry-breaking magnetic order which directly induces a ferroelectric polarization through various mechanisms, such as the spin-current or the inverse Dzyaloshinskii-Moriya effect. This intrinsic coupling between the magnetic and dipolar order parameters results in record-strength magnetoelectric effects [2]. In this context, there has been a recent surge of interest in 2D materials possessing such intrinsic multiferroic properties, enabling the integration and control of magnetoelectric effects in artificial heterostructures and nanoelectronic devices [3,4].
In this talk, I will present our recent study and realization of type-II multiferroic order in a single atomic layer of the transition metal-based van der Waals material NiI2 [5]. The multiferroic state of NiI2 is characterized by an inversion-symmetry-breaking helimagnetic order which induces a chirality-dependent electrical polarization. Using circular dichroic Raman measurements, we directly probed the magneto-chiral ground state and its electromagnon modes originating from dynamic magnetoelectric coupling. Using birefringence and second-harmonic generation measurements, we observed a highly anisotropic electronic state simultaneously breaking three-fold rotational and inversion symmetry to support polar order. The evolution of the optical signatures as a function of temperature and layer number surprisingly revealed an ordered magnetic, polar state that persists down to the ultrathin limit of monolayer NiI2 [6].
[1] Matsukura, F., Tokura, Y. and Ohno, H., Nat. Nanotech. 10, 209 (2015).
[2] Spaldin, N. A. and Ramesh, R., Nat. Mater. 18, 203 (2019).
[3] Huang, B., et al., Nat. Nanotech. 13, 544 (2018).
[4] Jiang, S., Li, L., Wang, Z., Mak, K. F. and Shan, J., Nat. Nanotech. 13, 549 (2018).
[5] Kurumaji, T., et al., Phys. Rev. B 87, 014429 (2013).
[6] Song, Q., et al., Nature 602, 601 (2022)
In this talk, I will present our recent study and realization of type-II multiferroic order in a single atomic layer of the transition metal-based van der Waals material NiI2 [5]. The multiferroic state of NiI2 is characterized by an inversion-symmetry-breaking helimagnetic order which induces a chirality-dependent electrical polarization. Using circular dichroic Raman measurements, we directly probed the magneto-chiral ground state and its electromagnon modes originating from dynamic magnetoelectric coupling. Using birefringence and second-harmonic generation measurements, we observed a highly anisotropic electronic state simultaneously breaking three-fold rotational and inversion symmetry to support polar order. The evolution of the optical signatures as a function of temperature and layer number surprisingly revealed an ordered magnetic, polar state that persists down to the ultrathin limit of monolayer NiI2 [6].
[1] Matsukura, F., Tokura, Y. and Ohno, H., Nat. Nanotech. 10, 209 (2015).
[2] Spaldin, N. A. and Ramesh, R., Nat. Mater. 18, 203 (2019).
[3] Huang, B., et al., Nat. Nanotech. 13, 544 (2018).
[4] Jiang, S., Li, L., Wang, Z., Mak, K. F. and Shan, J., Nat. Nanotech. 13, 549 (2018).
[5] Kurumaji, T., et al., Phys. Rev. B 87, 014429 (2013).
[6] Song, Q., et al., Nature 602, 601 (2022)
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Publication: Song, Q., et al. Evidence for a single-layer van der Waals multiferroic. Nature 602, 601–605 (2022). https://doi.org/10.1038/s41586-021-04337-x
Presenters
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Riccardo Comin
Massachusetts Institute of Technology MIT, Massachusetts Institute of Technology
Authors
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Riccardo Comin
Massachusetts Institute of Technology MIT, Massachusetts Institute of Technology