  The Josephson supercurrent in a Nb-InAs nanowire-Nb junction was studied
experimentally. The nanowire goes superconducting due to the proximity effect,
and can sustain a phase coherent supercurrent. An unexpected modulation of the
junction critical current in an axial magnetic field is observed, which we
attribute to a novel form of Josephson interference, due to the multi-band
nature of the nanowire. Andreev pairs occupying states of different orbital
angular momentum acquire different superconducting phases, producing
oscillations of the critical current versus magnetic flux. We develop a
semi-classical multi-band model that reproduces the experimental data well.
While spin-orbit and Zeeman effects are predicted to produce similar behaviour,
the orbital effects are dominant in the device studied here. This interplay
between orbital states and magnetic field should be accounted for in the study
of multi-band nanowire Josephson junctions, in particular, regarding the search
for signatures of topological superconductivity in such devices.
