Majorana entropy revival via tunneling phases

Abstract

Measuring the Majorana entropy ${S}_{M}={k}_{B}log({2}^{\frac{1}{2}})$ (where $log$ is the natural logarithm) may uniquely reveal whether an initial equilibrium state of a nanoscale device has a Majorana nature, and subsequent operations deal with an essentially nonlocal pair of non-Abelian Majorana bound states and not with trivial or other accidental non-Abelian states. However, in realistic setups both Majorana modes are inevitably involved in tunneling processes. We show that even when the tunneling amplitude of one Majorana mode is significantly suppressed, the Majorana entropy is ruined, and straightforward experiments will, in general, detect entropy $S\ensuremath{\ll}{S}_{M}$. To avoid this general problem we present a mechanism of the Majorana entropy revival via the tunneling phases of the Majorana modes and demonstrate that to successfully observe the universal Majorana plateau $S={S}_{M}$ one should intelligently tune the tunneling phases instead of leaving them uncontrolled. Practical feasibility of appropriate Majorana entropy measurements is supported by an example with parameters well achievable in modern labs.