Phase Signature of Topological Transition in Josephson Junctions

Topological superconductivity holds promise for fault-tolerant quantum computing. While planar Josephson junctions are attractive candidates to realize this exotic state, direct phase measurements as the fingerprint of the topological transition are missing. By embedding two gate-tunable Al/InAs Josephson junctions in a loop geometry, we measure a pi jump in the junction phase with an increasing in-plane magnetic field B-parallel to. This jump is accompanied by a minimum of the critical current, indicating a closing and reopening of the superconducting gap, strongly anisotropic in B-parallel to. Our theory confirms that these signatures of a topological transition are compatible with the emergence of Majorana bound states.

Automated summary

The research involves embedding two gate-tunable Al/InAs Josephson junctions in a loop geometry, where a pi jump in the junction phase is observed with an increasing in-plane magnetic field. This jump, accompanied by a minimum of the critical current, suggests a closing and reopening of the superconducting gap, showing strong anisotropy. The study's theory confirms that these signatures of a topological transition are consistent with the emergence of Majorana bound states.