The nature of superconductivity in the transition metal dichalcogenide family, particularly $2{\mathrm{H}\text{−}\mathrm{NbSe}}_2$ and $2{\mathrm{H}\text{−}\mathrm{TaS}}_2$ in the ultrathin limit, is not fully understood. While tunneling measurements apparently show a single superconducting gap, its detailed shape cannot be reproduced by simple single-band theories of superconductivity. In this work, we present tunneling data into thin exfoliated samples of both materials and show excellent agreement with the McMillan two-band model of superconductivity when the scattering parameters are large with respect to the superconducting gaps, even when only a single gap is apparent. We propose that in thin samples, these highly cross-scattering gaps reside on the $\mathrm{\Gamma }$ and $K$ Fermi surfaces derived from the transition metal atoms. Additionally, we quantitatively analyze pair breaking induced by magnetic field, and find that it is also well described by the two-band McMillan theory. Our results thus suggest that in its bulk thickness, $2{\mathrm{H}\text{−}\mathrm{NbSe}}_2$ is likely a three-band superconductor.

Close

PrevNext

View figure in article

• Multiband superconductivity
• Superconducting gap
• Superconducting order parameter
• Superconductivity
• s-wave
• 2-dimensional systems
• Superconducting devices
• Superconductors
• Transition metal dichalcogenides
• Tunnel junctions
• Type-II superconductors
• Unconventional superconductors
• Dilution refrigerator
• Resistivity measurements