The transmission of Cooper pairs between two weakly coupled superconductors
produces a superfluid current and a phase difference; the celebrated Josephson
effect. Because of time-reversal and parity symmetries, there is no Josephson
current without a phase difference between two superconductors. Reciprocally,
when those two symmetries are broken, an anomalous supercurrent can exist in
the absence of phase bias or, equivalently, an anomalous phase shift
φ0 can exist in the absence of a superfluid current. We report on the
observation of an anomalous phase shift φ0 in hybrid Josephson
junctions fabricated with the topological insulator Bi2Se3 submitted to
an in-plane magnetic field. This anomalous phase shift φ0 is observed
directly through measurements of the current-phase relationship in a Josephson
interferometer. This result provides a direct measurement of the spin-orbit
coupling strength and open new possibilities for phase-controlled Josephson
devices made from materials with strong spin-orbit coupling