Orbital selective Mott transition and magnetic moment in charge density wave heterostructures NbSe$_2/$Ta$X_2$

Abstract

We investigate the electronic properties of charge density wave (CDW) heterostructures out of monolayers of 1T-NbSe$_2$ and 1T-Ta$X_2$ (where, $X=$ S and Se) using first-principles followed by dynamical calculations. The CDW-ordered crystal structures are simulated using $\sqrt{13}\times\sqrt{13}$ supercells of NbSe$_2$ and Ta$X_2$. These two-dimensional heterostructures are modeled by stacking monolayers of NbSe$_2$ and Ta$X_2$ along (001) direction. Our investigations reveal the presence of non-zero magnetic moments in NbSe$_2/$TaS$_2$, albeit without a long-range magnetic order, raising the issue of a possible quantum spin liquid (QSL) as suggested for monolayer 1T-TaS$_2$ recently. In contrast, the NbSe$_2/$TaSe$_2$ heterostructure exhibits no magnetic moment. In order to capture the dynamical effects of local correlation, we use DFT plus multi-orbital dynamical mean field theory (MO-DMFT). Our findings indicate that NbSe$_2/$TaS$_2$ is considerably influenced by the dynamic corrections, whereas NbSe$_2/$TaSe$_2$ shows minimal effects. Additionally, an orbital-selective Mott transition (OSMT) is observed in the NbSe$_2/$TaS$_2$ bilayer heterostructure.