Possible Spin-Density Wave on Fermi Arc of Edge State in Single-Component Molecular Conductors [Pt(dmdt)₂] and [Ni(dmdt)₂]

We construct three-orbital tight-binding models describing single-component molecular conductors [Pt(dmdt)$_2$] and [Ni(dmdt)$_2$] using first-principles calculations. We show that [Ni(dmdt)$_2$] is a Dirac nodal line system with highly one-dimensional edge states at the (001) edge, similar to [Pt(dmdt)$_2$], as demonstrated in prior studies. To investigate possible edge magnetism, we calculate longitudinal and transverse spin susceptibilities using real-space-dependent random-phase approximation (RPA) in three-orbital Hubbard models in the presence of spin--orbit coupling. We find that the edge spin-density wave (SDW) is induced by the Coulomb repulsion and incommensurate nestings of the Fermi arcs. We also find that the magnetic structure of the edge SDW can be changed via extremely small carrier doping, which is controllable in molecular conductors.