Attosecond Carrier Dynamics in Quasi-2D SnS$_{\mathrm{2}}$

The electronic structure of SnS$_{\mathrm{2}}$, a van der Waals layered semiconductor with minimal spin-orbit splitting and an indirect bandgap in the visible, is highly anisotropic. Here, we investigate ultrafast carrier dynamics in SnS$_{\mathrm{2}}$ as a means to assess intra- and inter-layer coupling. Using resonant photoemission spectroscopy, we show that carrier dynamics in SnS$_{\mathrm{2}}$ are indeed highly anisotropic. Strong intralayer coupling leads to attosecond carrier dynamics within a layer, while interlayer coupling is much weaker and interlayer hopping occurs on much longer time-scales. These differences arise from the different orbitals contributing to the intra- and inter-layer coupling. Our study highlights with atomic detail the different time-scales involved in charge delocalization dynamics in layered materials and paves the way for tailoring layer-to-layer interactions.