Nature: Particles that are their own antiparticles were predicted by Ettore Majorana in 1937. None have been found in particle-physics experiments so far, but hints of Majorana-like quasiparticles have been seen in a condensed-matter system of strongly interacting electrons. Further, stronger evidence of the quasiparticles comes from a new experiment performed by Ali Yazdani of Princeton University and his colleagues. To create the quasiparticle, they placed a chain of iron atoms on top of a superconductor in such a way that the electrons in the iron atoms paired off. Each pair coordinated spins so that one of the electrons acted like a positron (the antielectron particle). The arrangement left unpaired electrons at both ends of the chain, which forced those two electrons to individually behave as both an electron and a positron. The finding strengthens the idea that true Majorana particles could exist outside of superconductors.
His 1988 sketch of how to use Antarctic ice to detect neutrinos led to the IceCube Neutrino Observatory, which made the first detections of high-energy neutrinos in 2013.