  It is believed that the edges of a chiral p-wave superconductor host Majorana
modes, relating to a mysterious type of fermions predicted seven decades ago.
Much attention has been paid to search for p-wave superconductivity in
solid-state systems, including recently those with strong spin-orbit coupling
(SOC). However, smoking-gun experiments are still awaited. In this work, we
have performed phase-sensitive measurements on particularly designed
superconducting quantum interference devices constructing on the surface of
topological insulators Bi2Te3, in such a way that a substantial portion of the
interference loop is built on the proximity-effect-induced superconducting
surface. Two types of Cooper interference patterns have been recognized at low
temperatures. One is s-wave like and is contributed by a zero-phase loop
inhabited in the bulk of Bi2Te3. The other, being identified to relate to the
surface states, is anomalous for that there is a phase shift between the
positive and negative bias current directions. The results support that the
Cooper pairs on the surface of Bi2Te3 have a 2\pi Berry phase which makes the
superconductivity p_x+ip_y-wave-like. Mesoscopic hybrid rings as constructed in
this experiment are presumably arbitrary-phase loops good for studying
topological quantum phenomena.
