  Tailoring interlayer coupling has emerged as a powerful tool to tune the
electronic structure of van der Waals (vdW) bilayers. One example is the usage
of the moire pattern to create controllable two-dimensional electronic
superlattices through the configurational dependence of interlayer electronic
couplings. This approach has led to some remarkable discoveries in twisted
graphene bilayers, and transition metal dichalcogenide (TMD) homo- and
hetero-bilayers. However, a largely unexplored factor is the interlayer
distance, d, which can impact the interlayer coupling strength exponentially.
In this letter, we quantitatively determine the coupling strengths as a
function of interlayer spacing at various critical points of the Brillouin zone
in bilayer MoS2. The exponential dependence of the coupling parameter on the
gap distance is demonstrated. Most significantly, we achieved a 280%
enhancement of K-valley coupling strength with an 8% reduction of the vdW gap,
pointing to a new strategy in designing a novel electronic system in vdW
bilayers.
