  Layered van der Waals (vdW) materials are emerging as one of the most
versatile directions in the field of quantum condensed matter physics. They
allow an unprecedented control of electronic properties via stacking of
different types of two-dimensional (2D) materials. A fascinating frontier,
largely unexplored, is the stacking of strongly-correlated phases of matter in
vdW materials. Here, we study 4Hb-TaS$_2$, which naturally realizes an
alternating stacking of a Mott insulator, recently reported as a gapless
spin-liquid candidate(1T-TaS$_2$), and a 2D superconductor (1H-TaS$_2$). This
raises the question of how these two components affect each other. We find a
superconducting ground state with a transition temperature of 2.7K, which is
significantly elevated compared to the 2H polytype (Tc=0.7K). Strikingly, the
superconducting state exhibits signatures of time-reversal-symmetry breaking
abruptly appearing at the superconducting transition, which can be naturally
explained by a chiral superconducting state.
