Spin-Orbit induced phase-shift in Bi2Se3 Josephson junctions

Overview & Synopsis

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 φ 0 can exist in the absence of a superfluid current. We report on the observation of an anomalous phase shift φ 0 in hybrid Josephson junctions fabricated with the topological insulator Bi 2 Se 3 submitted to an in-plane magnetic field. This anomalous phase shift φ 0 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.