Superconducting tunneling study of vanadium

Abstract

The tunneling spectroscopy of McMillan and Rowell is extended to vanadium, with the use of clean and highly ordered structures of the form $M$- ${\mathrm{Al}}_2$ ${\mathrm{O}}_3$-Al/V. The Eliashberg function ${\alpha }^{2}F\left(E\right)\mathrm{}$ is determined and leads to $\lambda =0.82\mathrm{}\pm 0.05$ and ${\mu }_{\mathrm{ph}}^{*}=0.15\mathrm{}\pm 0.03$. These tunneling results, the first available for V, indicate a smaller influence of paramagnon spin fluctuations in suppressing superconductivity in vanadium than recently suggested, but do not rule out such effects at a level ${\lambda }_s\sim 0.1$.