Paper detail

A new class of intrinsic magnet: two-dimensional yttrium sulphur selenide

Exploring and controlling magnetism in two-dimensional (2D) layered magnetic crystals, as well as their inclusion in heterogeneous assemblies, provide an unprecedented opportunity for fundamental science and technology. To date, however, there are only a few known intrinsic 2D magnets. Here we predict a novel 2D intrinsic magnet, yttrium sulfur selenide (YSSe), using first-principles calculations. The magnetism of this transition metal dichalcogenide originates from the partially-filled $3p$- and $4p$-orbitals of the chalcogens, unlike other known intrinsic magnets where magnetism arises from the partially-filled $3d$- and $4f$-orbitals. The unconventional magnetism in YSSe is a result of a unique combination of its structural and electronic properties. We further show that a lack of mirror symmetry results in piezoelectric properties, while the broken space- and time-symmetry ensures valley polarization. YSSe is a rare magnetic-piezoelectric material that can enable novel spintronics, valleytronics, and quantum technologies.