Non-equilibrium Majorana fluctuations

Non-equilibrium physics of random events, or fluctuations, is a unique fingerprint of a given system. Here we demonstrate that in non-interacting systems with dynamics driven essentially by Majorana states the effective charge e*, characterizing the electric current fluctuations, is fractional. This is in contrast to non-interacting Dirac systems with the trivial electronic charge e* = e. In the Majorana state, however, we predict two different fractional effective charges at low and high energies, e(1)* = e/2 e(h)* = 3e/2, accessible at low and high bias voltages, respectively. Weshow that while the lowenergy effective charge e(1)* is sensitive to thermal fluctuations of the current, the high-energy effective charge e(h)* is robust against thermal noise. A unique fluctuation signature of Majorana fermions is therefore encoded in the high- voltage tails of the electric current noise easily accessible in experiments on strongly non- equilibrium systems even at high temperatures.