Nonequilibrium Josephson Current

Abstract

Control of a supercurrent in weak-link Josephson junctions can be realized by two alternative methods. The first approach, which was described in the preceding chapter, is to control the carrier concentration in the semiconductor with a gate electrode. A typical example of this kind of structure is the Josephson field effect transistor. In this chapter we shall discuss how a Josephson supercurrent can be controlled by injecting nonequilibrium carriers. As explained in Sect. 6.1, the net supercurrent is partially determined by the occupation of Andreev bound states located energetically within the superconductive gap. If carriers are injected, the occupation of these Andreev levels is altered. This directly affects the net supercurrent in the junction. In the first part of this chapter the underlying theoretical models will be discussed in detail, while in the second part the corresponding experiments are described.