Nonequilibrium Majorana fluctuations

TL;DR

This paper predicts that noninteracting systems with Majorana states exhibit fractional effective charges in current fluctuations, with distinct low and high energy values, providing a unique experimental signature of Majorana fermions.

Contribution

It introduces the novel prediction of fractional effective charges in Majorana systems and distinguishes their thermal sensitivity, offering a new way to identify Majorana states through noise measurements.

Findings

Low energy effective charge e*_l = e/2 is thermally sensitive.

High energy effective charge e*_h = 3e/2 is thermally robust.

High voltage noise signatures reveal Majorana fermions even at high temperatures.

Abstract

Nonequilibrium physics of random events, or fluctuations, is a unique fingerprint of a given system. Here we demonstrate that in noninteracting systems, whose dynamics is driven by Majorana states, the effective charge $e^*$, characterizing the electric current fluctuations, is fractional. This is in contrast to noninteracting Dirac systems with the trivial electronic charge, $e^*=e$. Quite the opposite, in the Majorana state we predict two different fractional effective charges at low and high energies, $e^*_l=e/2$ and $e^*_h=3e/2$, accessible at low and high bias voltages, respectively. We show that while the low energy effective charge $e^*_l$ 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 nonequilibrium systems even at high temperatures.