Nonequilibrium transport of InAs/GaAs(111)A heterostructures coupled with superconducting Nb electrodes
We have investigated the nonequilibrium transport of a two-dimensional electron gas (2DEG) in an InAs/GaAs(111)A heterostructure coupled with superconducting Nb electrodes. In the superconductor (S)/normal conductor (N) hybrid system, the transport properties of the N are affected by the superconducting proximity effect. According to the updated theory, this proximity correction to the conductance (PCC) shows the reentrant behaviour to be a function of energy. We observed reentrant behaviour in the voltage and temperature dependences of the conductance of the 2DEG. The conductance peak is observed at Tcmax ~ 6 K and the PCC reaches ~20% of the normal-state conductance and almost disappears at low energies. These values are one order of magnitude higher than those obtained in the previous works. These results are most likely achieved by diminishing the length of the N channel L because the PCC as well as the correlation energy (Thouless energy) is proportional to 1/L2. The measured conductance showed a very good agreement with that of the theory.