Fig. 3: Magnetic field interference patterns reflecting spatial quantum interference.

a,c,e, Josephson critical current I_c versus magnetic field \(\mu _0H_ \bot\) plots for the d_s = 28 (a), 80 (c) and 119 nm (e) Nb/Mn₃Ge/Nb junctions, taken at a fixed T = 2 K. In these measurements, \(\mu _0H_ \bot\) is applied perpendicular to the interface plane of the Nb electrodes. The top inset displays the current–voltage I–V curve of each junction around zero-order minimum of I_c(\(\mu _0H_ \bot\)). The bottom inset in a schematically illustrates the effective junction area \(A_{\mathrm{{flux}}}^{\mathrm{{eff}}}\) of magnetic flux penetration, given by \(\left( {2\lambda _L + d_{\mathrm{s}}} \right)w\). Here λ_L is the London penetration depth of the Nb electrodes and w is the width of the Mn₃Ge spacer. b,d,f, Data equivalent to a,d,e but for the magnetic field \(\mu _0H_{||}\) applied parallel to the interface plane of the Nb electrodes for d_s = 28 (b), 80 (d) and 119 nm (f). Note that, accordingly, \(A_{\mathrm{{flux}}}^{\mathrm{{eff}}}\) changes to \(\left( {2\lambda _L + d_{\mathrm{s}}} \right)t\) where t is the effective thickness of the Mn₃Ge spacer.