  Majorana fermions have been intensively studied in recent years for their
importance to both fundamental science and potential applications in
topological quantum computing1,2. Majorana fermions are predicted to exist in a
vortex core of superconducting topological insulators3. However, they are
extremely difficult to be distinguished experimentally from other quasiparticle
states for the tiny energy difference between Majorana fermions and these
states, which is beyond the energy resolution of most available techniques.
Here, we overcome the problem by systematically investigating the spatial
profile of the Majorana mode and the bound quasiparticle states within a vortex
in Bi2Te3/NbSe2. While the zero bias peak in local conductance splits right off
the vortex center in conventional superconductors, it splits off at a finite
distance ~20nm away from the vortex center in Bi2Te3/NbSe2, primarily due to
the Majorana fermion zero mode. While the Majorana mode is destroyed by
reducing the distance between vortices, the zero bias peak splits as a
conventional superconductor again. This work provides strong evidences of
Majorana fermions and also suggests a possible route to manipulating them.
