Extended Data Fig. 9: Behaviour of the Josephson critical current at B|| = 0. | Nature

Extended Data Fig. 9: Behaviour of the Josephson critical current at B|| = 0.

From: Evidence of topological superconductivity in planar Josephson junctions

Extended Data Fig. 9

a, To investigate the behaviour of the Josephson current in our device, we measured the differential resistance R = dV/dI of the SQUID with a conventional four-probe technique by applying an a.c. bias Iac < 5 nA, superimposed on a variable d.c. bias Idc, to one of the superconducting leads of the interferometer. During these measurements the QPC was pinched off at Vqpc = V. The Josephson critical current of JJ1 can be measured independently by pinching off JJ2. b, Differential resistance R1 of JJ1 as a function of the Idc and V1 measured in device 2. The region of zero resistance indicates that a dissipationless Josephson current due to Cooper pair transport is flowing through the junction. c, R1 as a function of Idc and the out-of-plane field B displaying a characteristic Fraunhofer pattern, with a periodicity compatible with the area of JJ1 \({W}_{1}\times {L}_{1}\) ≈ 0.13 µm2. For both the measurements displayed in a and c, JJ2 was pinched off by setting the gate voltage V2 = 1.5 V. d, When JJ2 was open (V2 = 0), the differential resistance of the SQUID RSQUID showed periodic oscillations (periodicity of 250 µT, consistent with the area of the superconducting loop, 8 µm2) superimposed to the Fraunhofer patterns of both junctions. The ratio between the critical currents of the junctions at zero field is extracted from the average value of the SQUID critical current and the semi-amplitude of the SQUID oscillations, resulting in Ic,2(0)/Ic,1(0) = 5.2.

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