News and Events

The non-zero thickness of MoS₂ single layer (SL) manifests in electron states forming classes of states even and odd with respect to reflections through the central plane. These states are energetically well separated: in particular, we show that pristine MoS₂ SL exhibits two bandgaps Eg_|| =1.9 eV and Eg_(\perp)=3.2 eV for the optical in-plane and out-of-plane susceptibilities x_|| and x_(\perp), respectively. Because of this, odd states are often neglected, which effectively reduces MoS₂ SL to a perfect 2D system. We study states bound to defects in MoS₂ SL with three types of vacancy defects (VD): (i) Mo-vacancy, (ii) S2-vacancy, and (iii) 3xMoS₂ quantum antidot --- and show that odd states play an equally important role as even states. In particular, we show that odd states bound to VD lead to resonances in x_(\perp) inside Eg_(\perp) in MoS₂ SL with VDs. Additionally, we demonstrate that the states bound to VDs are not necessarily confined to the bandgap in the even subsystem, which requires the extension of the energy region affected by the bound states. The resulting optical signatures not only provide the possibility to identify the type but also the concentration of VDs, thereby paving the way to quantifying the purity of defected SLs of transition metal dichalcogenides containing VDs.