Spin-valley polarization in NbSe₂ at van der Waals interface

Van der Waals materials attract growing interest as a site for the emergence of various two-dimensional (2D) properties, including luminescence properties, 2D superconductivity, 2D magnetism, and topological quantum conduction. One of the essential factors that have supported the development of vdW materials research is the symmetry breaking of the crystal structure unique to vdW materials. Among them, transition metal dichalcogenides (TMDs) with H-type polymorphism have a unique Zeeman-type spin-orbit interaction (SOI), which reflects the broken spatial inversion symmetry in the monolayer limit. A variety of novel properties coupled to the Zeeman-type SOI have been reported, such as valley-polarized luminescence and transport properties in semiconductor TMDs such as MoS₂ and WSe₂, and unconventional superconductivity in metal TMDs such as NbSe₂ and TaS₂. Here, we have focused on the effect of Zeeman-type SOI on magnetic properties and have reported the ferromagnetic modulation by Zeeman-type SOI in the heterostructure of NbSe₂ with Zeeman-type SOI and ferromagnetic vanadium selenide¹.

On the other hand, in the above heterostructure, not only the magnetic side was modulated by NbSe₂ (Zeeman-type SOI), but also the electronic state of the NbSe₂ side was modulated by the magnetism. In particular, when the magnetization is induced in NbSe₂ through the interface proximity effect, the band modulation by magnetization and Zeeman-type SOI was coupled and a state called ferro-valley ferromagnetism was realized². In this presentation, we will discuss the transport properties of the ferro-valley ferromagnetic state revealed through the details of the transport properties of this heterostructure.