Spin systems in transition metal phosphous trichalcogenide van der Waals materials

Efrat Lifshitz

Technion

Magnetism is a topic of a wide interest since the discoveries of motors/generators, through magneto-resistance and up to modern times, where low dimensional materials offer a support for new magnetic phenomena. The talk will focus on the influence of magnetic moments and magnetism on the optical magneto-properties of semiconductors in an ultimate two-dimensional limit found in van der Waals transition metal phosphorous tri-chalcogenides. A few types of magnetic properties will be discussed: the long-range magnetic order, ferromagnetism, anti-ferromagnetism or special spin textures; an interfacial developed Rashba spin-orbit effect; nuclear spin Overhauser effect; magnetic polaron, all gaining special stabilization by the size confinement and a shape anisotropy. The mentioned intrinsic fields lead to a lift of energy or momentum degeneracy at band-edge states with selective spin orientation in the ground or/and excited state, being of a special interest in emerging technologies of spin-electronics and quantum computation. The lecture will include the study of long-range magnetic order and valley effects in single layer of metal phosphor tri-chalcogenide compounds. Metal phosphor tri-chalcogenides with the general chemical formula MPX3 (M=metal, X=chalcogenide) closely resembling the metal di-chalcogenides, but the metal being paramagnetic elements, while one-third of them are replaced by phosphor pairs. The metal ions within a single layer produce a ferromagnetic or anti-ferromagnetic arrangement, endowing those materials with unique magnetic and magneto-optical properties. Most recent magneto-optical measurements will be reported, exposing the existence of valley degree of freedom in a few MPX3 (e.g., FePS3, MnPS3), that reveals a protection of the spin helicity of each valley however, the coupling to an anti-ferromagnetism lifts the valleys' energy degeneracy. The phenomenon was also examined in magnetically doped diamagnetic MPX3 layers. The results indicated the occurrence of coupling between photo-generated carriers and magnetic impurities and the formation of magnetic polaron.

[1] A.K. Budniak, N.A. Killilea, S.J. Zelewski, M. Sytnyk, Y. Kauffmann, Y. Amouyal, R. Kudrawiec, W. Heiss, E. Lifshitz; Small, 2020, 16 (1), 1905924
[2] M. Shentcis, A.K. Budniak, R. Dahan, Y. Kurman, X. Shi, M. Kalina, H.H. Sheinfux, M. Blei, M.K. Svendsen, Y. Amouyal, F. Koppens, S. Tongay, K.S. Thygesen, E. Lifshitz, F.J.G. de Abajo, L.J. Wong, I. Kaminer; Under revision in Nature Photonics