  The layered Mott insulator ${\alpha}$-RuCl${_3}$ has been extensively studied
as a potential Kitaev quantum spin liquid candidate. Here, by constructing
heterostructures with graphite, we employed electron tunneling measurements on
few-layer ${\alpha}$-RuCl${_3}$ using a scanning tunneling
microscopy/spectroscopy. Characteristic tunneling spectra were detected on
${\alpha}$-RuCl${_3}$ layers in proximity to graphite. In the single-layer
${\alpha}$-RuCl${_3}$ in direct contact with graphite, distinct states in the
Mott-gap regime were observed. The in-gap states are demonstrated to be closely
related to the electron orbitals in ${\alpha}$-RuCl${_3}$ and graphite, and to
be sensitive to interfacial coupling, where a hybridization at the
heterointerface is hypothesized. The in-gap states are also thought of as a
charge reservoir for weakly doping the ${\alpha}$-RuCl${_3}$ upper-layers. It
demonstrated that the weak doping effect causes a considerable decrease in the
Mott-gap within the upper-layers, suggesting that an unconventional
Mott-transition is occurring in these layers. The results show that the
heterostructure comprised of ${\alpha}$-RuCl${_3}$ and graphite is a good
platform for investigating the doping physics in ${\alpha}$-RuCl${_3}$.
Therefore, tunneling into such a doped system is a useful probe for studying
otherwise insulating spin-liquid candidates.
