Superconducting density of states and vortex lattice of LaRu$_2$P$_2$ observed by Scanning Tunneling Spectroscopy

Abstract: We provide the superconducting density of states of the iron based superconductor LaRu2P2 (Tc= 4.1 K), measured using millikelvin Scanning Tunneling Microscopy. From the tunneling conductance, we extract a density of states which shows the opening of a s-wave single superconducting gap. The temperature dependence of the gap also follows BCS theory. Under magnetic fields, vortices present Caroli de Gennes Matricon states, although these are strongly broadened by defect scattering. From the vortex core size we obtain a superconducting coherence length of ξ = 50 nm, compatible with the value extracted from macroscopic Hc2 measurements. We discuss the comparison between s-wave LaRu2P2 and pnictide unconventional multiple gap and strongly correlated Fe based superconductors.