Vertical quantum confinement in bulk MoS${}_2$

Abstract

We experimentally observe quantum confinement states in bulk MoS${}_2$ using Angle-Resolved Photoemission Spectroscopy (ARPES). The band structure at the $\overline{\Gamma }$ point reveals quantum well states (QWSs) linked to vertical quantum confinement of the electrons, confirmed by the absence of dispersion in k${}_z$ and a strong intensity modulation with photon energy. Notably, the binding energy dependence of the QWSs vs $n$ does not follow the quadratic dependence of a two-dimensional electron gas. Instead, a linear behaviour is observed that is consistent with a parabolic-like quantum well. This confinement arises from the mechanical exfoliation preparation method, which leads to the detachment of a multilayer stack from the underlying bulk. This is confirmed by Density Functional Theory (DFT) calculations. The quantum confinement in bulk-like MoS${}_2$ not only offers the opportunity to explore intersubband transitions to exploit optical properties but also provides a means to study fundamental quantum phenomena in multilayer stacks of different thicknesses.

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