Andreev pair injection into a transition metal dichalcogenide monolayer

This is the authors' abstract. We don't add key points for this paper.

We demonstrate Andreev pair injection across Nb-WS2 junction evident as Andreev reflection in differential conductivity spectra below Nb critical temperature Tc . The superconducting- 2D semiconducting junction defined by a focused ion beam, shaped Nb pads, and semi-dry transfer of single layer CVD-grown WS2 crystals ensured the mechanical integrity of the 2D TMD film, reduced contamination and defects at Nb-WS2 junction, enabling the pristine study of the interface and facilitating Andreev pair injection. We observed enhanced conductivity in dI/dV spectra for junction voltages smaller than the corresponding Nb superconducting gap, which vanishes as the device temperature is increased above the Tc . The position and the temperature dependence of the conductivity peaks suggest proximity effect-related phenomena explained by developed modified BTK theory. The presented results are crucial for the future implementation of proximity-based 2D hybrid devices including quantum light sources and superconducting field-effect transistors based on superconductor-semiconductor junctions.