  The recent development of superconducting spintronics has revealed the
spin-triplet superconducting proximity effect from a spin-singlet
superconductor into a spin-polarized normal metal. In addition recently
superconducting junctions using semiconductors are in demand for highly
controlled experiments to engineer topological superconductivity. Here we
report experimental observation of Andreev reflection in junctions of
spin-resolved quantum Hall (QH) states in an InAs quantum well and the
spin-singlet superconductor NbTi. The measured conductance indicates a sub-gap
feature and two peaks on the outer side of the sub-gap feature in the QH
plateau-transition regime increases. The observed structures can be explained
by considering transport with Andreev reflection from two channels, one
originating from equal-spin Andreev reflection intermediated by spin-flip
processes and second arising from normal Andreev reflection. This result
indicates the possibility to induce the superconducting proximity gap in the
the QH bulk state, and the possibility for the development of superconducting
spintronics in semiconductor devices.
