Proximity effect of iron-based superconductor in conventional $s$-wave superconducting thin films

The proximity effect has been proposed as a mechanism to unambiguously identify the possible $s_{\pm}$-state in iron-based superconductors.\footnote{A. E. Koshelev, V. Stanev, Europhysics Letters, Vol. 96, 27014 (2011)} With a thin $s$-wave superconductor atop a $s_{\pm}$-superconductor it is suggested that the $s$-wave order parameter will couple to the $s_{\pm}$-gaps differently, inducing a correction to the $s$-wave density of states that can be probed using electron tunneling spectroscopy. In this talk, we will present recent results of the superconducting proximity effect in s-wave MoGe thin films sputtered on top of bulk superconducting Ba$_{0.6}$K$_{0.4}$Fe$_{2}$As$_{2}$ (T$_{c}$=35K) pnictide. Electron tunneling spectroscopy measurements were performed for several MoGe film thicknesses using a homemade point contact setup. Finally, results will also be presented for similar measurements using two conventional $s$-wave superconductors.