  Strongly correlated materials exhibit exotic electronic states arising from
the strong correlation between electrons. Dimensionality provides a tuning knob
because thinning down to atomic thickness reduces screening effects and
enhances electron correlations. In this work, a 2D Kondo lattice has been
created by stacking a layer of 1T-TaS2 on a 2H-TaS2 crystal, which are bound by
weak van der Waals interactions. By using high-resolution scanning tunnelling
spectroscopy and density functional theory, we unambiguously demonstrate the
formation of a 2D Kondo lattice from an ensemble of independent Kondo
impurities present at higher temperatures. The possibility to create 2D Kondo
lattices in van der Waals heterostructures paves the way for the exploration of
unconventional metallic, magnetic and superconducting states not present in
more standard correlated materials.
