Enhanced Critical Magnetic Field For Monoatomic-Layer Superconductor By Josephson Junction Steps

We have studied the monoatomic-layer superconductors formed on semiconducting substrates and investigated the role of steps in superconducting properties. In the present study we found that the steps of the Si(111)-root 3 x root 43 Pb reconstructed structure significantly disrupt the electronic states of the superconducting atomic layer and hold Josephson-like vortices under the out-of-plane magnetic field. Because of the strong decoupling, narrow terraces whose width is less than three times the coherence length behave like superconducting nano stripes and exhibit large critical field against the out-of-plane magnetic field. Since monolayer superconductors are intrinsically strong against in-plane magnetic field, superconducting materials highly tolerant against magnetic fields in all directions might be tailored by controlling the step arrangement in the atomic-layer superconductors.