This graph shows the flow of electrical current without developing a voltage (supercurrent) through a semiconductor coupled to two superconductors. The size of the maximum supercurrent (called critical current) can be controlled by a voltage on a nearby electrode (gate).
Seeing this effect is important for building up to Majorana fermion experiments. It has been reported first in this paper from 2005. So we are steadily catching up with state-of-the-art (Coulomb blockade from a couple of posts ago was first demonstrated in the 1980-ies).