The reports in this issue about half-quantum vortices in strontium ruthenate (page 17) and about spin–orbit coupling in a nanowire (page 19) both involve a system in which theorists have proposed that one might find an elusive Majorana particle. A system of Majorana particles might be a good candidate for a topological quantum computer.
Before his mysterious disappearance in 1938, the young Italian theorist Ettore Majorana had modified Dirac’s equations for spin-1⁄2 particles such as electrons and holes. In Majorana’s modification, the creation and annihilation operators for particles are self conjugate and the resulting Majorana particles are their own antiparticles. To date, no one has identified a physical realization of those exotic objects, although neutrinos are leading candidates.1 Others include supersymmetric partners of known bosons and constituents of dark matter.
Recently the search has broadened to include a number of solid-state systems. Some theorists have...
