  Van der Waals heterostructures (vdWHs) allow the assembly of high-crystalline
two-dimensional (2D) materials in order to explore dimensionality effects in
strongly correlated systems and the emergence of potential new physical
scenarios. In this work, it is illustrated the feasibility to integrate 2D
materials in-between 2D superconductors. Particularly, it is presented the
fabrication and electrical characterization of vertical vdWHs based on
air-unstable atomically-thin transition metal dichalcogenides formed by
NbSe2/TaS2/NbSe2 stacks, with TaS2 being the insulator 1T-TaS2 or the metal
2H-TaS2. Phase transitions as 1T-TaS2 charge density wave and NbSe2
superconductivity are detected. An enhancement of the vdWH resistance due to
Andreev reflections is observed below the superconducting transition
temperature of the NbSe2 flakes. Moreover, in the NbSe2 superconducting state,
the field and temperature dependence of the normalized conductance is analyzed
within the Dynes' model and the overall behavior is consistent with the
Bardeen-Cooper-Schrieffer theory. This vdWH approach can be extended to other
2D materials, such as 2D magnets or topological insulators, with the aim of
exploring the new emergent properties that may arise from such combinations.
