The influence intrinsic magnetic fields on the optical properties of two-dimensional semiconductors

Sun, 12/06/202212:15
12:15 | Seminar Hall, Los Angeles Building, entrance floor

Prof. Efrat Lifshitz

Schulich Faculty of Chemistry, Solid State Institute, and the Helen Diller Quantum Information Center, Russell Berrie Nanotechnology Institute, Technion, Haifa, Israel


Magnetism is a topic of wide interest since the discoveries of motors/generators, through magneto-resistance and up to modern times, where low dimensional materials offer 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 tri-chalcogenides and perovskite nanoplatelets. 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 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 special interest in emerging technologies of spin-electronics and quantum computation.


Long-range magnetic order in 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 dual relation between magnetism and electronic properties.

Rashba and Overhauser effects in perovskite materials: Perovskite materials are composed of organic-inorganic or all inorganic constituents.  They mostly contain octahedral units of metal-halides or metal-oxides, generating an inorganic network with voids that are filled by organic or inorganic counter ions.  The studies to be reported are related to compounds with 2D and 3D morphologies. The magneto-optical properties of such compounds revealed selective exciton' circular polarization components following a non-linear energy split upon an increase of an applied external magnetic field, which was associated with the involvement of a Rashba effect. Furthermore, the degree of circular polarization dependence on the applied magnetic field exposed a trend related to the Overhauser effect.