Abstract
Search for Majorana fermions renewed interest in semiconductor–superconductor interfaces, while a quest for higher-order non-Abelian excitations demands formation of superconducting contacts to materials with fractionalized excitations, such as a two-dimensional electron gas in a fractional quantum Hall regime. Here we report induced superconductivity in high-mobility two-dimensional electron gas in gallium arsenide heterostructures and development of highly transparent semiconductor–superconductor ohmic contacts. Supercurrent with characteristic temperature dependence of a ballistic junction has been observed across 0.6 μm, a regime previously achieved only in point contacts but essential to the formation of well separated non-Abelian states. High critical fields (>16 T) in NbN contacts enables investigation of an interplay between superconductivity and strongly correlated states in a two-dimensional electron gas at high magnetic fields.
Highlights
Introduction ofJosephson field effect transistor concept[1] sparked active research on proximity effects in semiconductors
Induced superconductivity and electrostatic control of critical current has been demonstrated in twodimensional gases in InAs2,3, graphene[4] and topological insulators[5,6,7,8], and in one-dimensional systems[9,10,11] including quantum spin Hall edges[12,13]
Interest in superconductor–semiconductor interfaces was renewed by the search for Majorana fermions[14,15], which were predicted to reside at the interface[16,17,18]
Summary
Introduction ofJosephson field effect transistor concept[1] sparked active research on proximity effects in semiconductors. Unlike in InAs, where Fermi level (EF) at the surface resides in the conduction band, in GaAs EF is pinned in the middle of the gap, which results in a high Schottky barrier between a 2DEG and a superconductor and low transparency non-ohmic contacts. We report the development of transparent superconducting ohmic contacts to high-mobility 2DEG in GaAs. The superconducting contact is type-II NbN with large critical field 416 T.
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