Nature Phys. 8, 887–895 (2012)

Majorana fermions — particles that are their own antiparticle — were first predicted in the 1930s, but such elementary particles have yet to be identified. In condensed matter, experiments have recently hinted at the existence of quasiparticles with Majorana-like states, which could, for example, be used as information carriers in robust quantum computation. However, definitive proof of these fermions also remains elusive. Moty Heiblum and colleagues at the Weizmann Institute of Science have now provided further evidence for the existence of Majorana states in a semiconducting nanowire.

When in proximity to a superconductor, a nanowire can enter a topological phase that is expected to host Majorana quasiparticles at both ends. The signature of Majorana states in the transport characteristics of the nanowire is a conductance peak of 2e2/h at zero applied bias, where e is the elementary charge and h is Planck's constant. Heiblum and colleagues observed the emergence of zero-bias peaks in an indium arsenide nanowire in contact with an aluminium superconductor as a function of applied magnetic field, chemical potential and temperature. The zero-bias peaks disappear when the magnetic field causes the superconducting gap to collapse, as expected for a Majorana state.

Although the measured zero-energy conductance has a smaller amplitude than the predicted value, and other mechanisms could give rise to similar transport features, the agreement between the experiments and numerical simulations strongly suggests the formation of Majorana states in the nanowire.