Suppression of Andreev reflection at energies well below the superconducting gap
We experimentally investigate transport properties of a single junction between a superconductor and the edge of a two-dimensional electron system in a narrow $In_{0.75}Ga_{0.25}As$ quantum well with strong Rashba-type spin-orbit coupling. We experimentally demonstrate suppression of Andreev reflection within a narrow energy range within the superconducting gap. This suppression is shown to be independent of the superconductor material and the interface disorder. The effect is only present at lowest temperatures and magnetic fields, far from the corresponding critical values of a superconducting transition. We connect the observed suppression with a spin-Hall effect due to a strong spin-orbit coupling on the normal side of the junction.