Semiconductor-coupled Josephson junctions with a submicron split gate electrode

The superconducting and normal transport in a semiconductor-coupled Josephson junction in the clean limit has been studied by using a junction whose channel is a high-mobility two-dimensional electron gas (2DEG) in the semiconductor heterostructure and that has a submicron split gate electrode on the channel. When the absolute value of negative gate voltage V-g is small, the critical current oscillates as a function of gate voltage, and this oscillation is due to Fabry-Perot interference of the quasiparticles. When the absolute value of V-g is large, the split gate defines a quantum point contact in the 2DEG. Andreev reflection leads to the reflected holes being focused to the quantum point contact and the current-voltage characteristics change from current-deficit to excess-current.