Electron-electron interactions, valleys, and band nesting in gated MoS₂ quantum dots.

We report on the effect of valley, spin and band nesting on the many-electron properties of gated MoS₂ quantum dots. We start with single electron atomistic calculation for a computational box with periodic boundary conditions containing up to 10⁶ atoms, using a tight binding model developed from ab-initio methods for MoS₂ [1,2]. The effect of the metallic gates is modelled as a parabolic lateral confining potential. We find a twofold degenerate energy spectrum of confined electrons originating from the two non-equivalent valleys K and -K as well as a sixfold degenerate ladder of states associated with six secondary conduction band minima Q [3]. These electronic states up to 5 K-derived shells are then populated with up to 6 electrons and electron-electron interactions are turned on. We demonstrate that the large intra-valley exchange interaction determines the many-electron ground state of these QDs. As a consequence, with varying QD size and confining potential, a valley-polarized and spin-polarised broken symmetry ground states emerge.
[1] T. Scrace, et al. Nature Nanotech. 10, 7, (2015), 603–607.
[2] M. Bieniek, M. Korkusinski, L. Szulakowska, P. Potasz, I. Ozfidan, and P. Hawrylak, PRB 97, 085153 (2018).
[3] M. Bieniek, L. Szulakowska, and P. Hawrylak, PRB, in review, (2019).