In 1937, physicist Ettore Majorana had predicted that in fermions, a group of sub-atomic particles that includes proton, neutron, electron, neutrino and quarks, there should be particles that are there own anti-particles—that is they would contain both their matter and anti-matter. Eighty years later, University of California and Stanford University scientists have announced the first concrete evidence of a Majorana fermion. Publishing their findings in the journal, Science, the scientists have predicted where exactly to find the Majorana fermion and what to look for as its “smoking gun” signature.
The physicist community has been looking for Majorana quasiparticles—particle-like excitations that are created because of the way electrons behave in superconducting materials—given the difficulty of the experiments to determine actual Majorana fermions. Scientists have reported signatures of quasiparticles, but these have been “bound” to one particular space rather than propagating in space and time.
That is, it was hard to determine whether these signatures resulted from quasiparticles or other effects. In the present experiment, the researchers stacked films of two quantum materials—a superconductor and a magnetic topological insulator that conducts electricity only along its surface and edges. This made the material a superconducting topological insulator that allowed electrons to flow along the two edges of the material’s surface. The magnetic nature of the material made electrons flow one way on one of the edges and the reverse way on the other edge. Sweeping another magnet over the stack made the electrons change direction.
At a certain point, Majorana quasiparticles came live and their paths were tracked. These paths mirrored the path of the electrons, but in steps exactly half as high as the ones the electrons took—the smoking gun. Though the quasiparticles may not exist in nature, Majorana fermions may one day form the backbone of robust quantum computing. Since each Majorana is half of a subatomic particle, information can be stored in two that are widely separated, decreasing the chance that something would knock out both at once.