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We demonstrate long-range superconducting correlations in a several micrometer-long carbon nanotube encapsulated in a van der Waals stack between hBN and NbSe$_2$. We show that a substantial supercurrent flows through the nanotube section beneath the NbSe$_2$ crystal as well as through the 2 $\mu$m-long section not in contact with it. As expected for superconductors of nanoscopic cross section, the current-induced breakdown of superconductivity is characterized by resistance steps due to the nucleation of phase slip centers. All elements of our hybrid device are active building blocks of several recently proposed setups for realization of Majorana fermions in carbon nanotubes., Comment: 11 pages, 6 figures

Raman spectroscopy is a precious tool for the characterization of van der Waals materials, e.g. for the determination of the layer number in thin exfoliated flakes. For sensitive materials, however, this method can be dramatically invasive. In particular, the light intensity required to obtain a significant Raman signal is sufficient to immediately photo-oxidize few-layer thick metallic van der Waals materials. In this work we investigated the impact of the environment on Raman characterization of thin NbSe$_2$ crystals. We show that in ambient conditions the flake is locally oxidized even for very low illumination intensity. On the other hand, we observe no degradation if the Raman measurements are performed either in vacuum or on fully hBN-encapsulated samples. Interestingly, we find that covering samples deposited on the usual SiO$_2$ surface only from the top is not sufficient to prevent diffusion of oxygen underneath the layers., 7 pages, 4 figures. Johannes Holler and Lorenz Bauriedl contributed equally to this work