  A phase from an adiabatic exchange of Majorana bound states (MBS) reveals
their exotic anyonic nature. For detecting this exchange phase, we propose an
experimental setup consisting of a Corbino-geometry Josephson junction on the
surface of a topological insulator, in which two MBS at zero energy can be
created and rotated. We find that if a metallic tip is weakly coupled to a
point on the junction, the time-averaged differential conductance of the
tip-Majorana coupling shows peaks at the tip voltages $eV = \pm (\alpha - 2\pi
l) \hbar/ T_J$, where $\alpha = \pi/2$ is the exchange phase of the two
circulating MBS, $T_J$ is the half rotation time of MBS, and $l$ an integer.
This result constitutes a clear experimental signature of Majorana fermion
exchange.
