Phase signature of topological transition in Josephson Junctions

William Mayer, Matthieu C. Dartiailh, Joseph Yuan, Kaushini S. Wickramasinghe, Alex Matos-Abiague, Igor Žutić, Javad Shabani

Published 2019-06-04Version 1

Topological superconductivity hosts exotic quasi-particle excitations including Majorana bound states which hold promise for fault-tolerant quantum computing. The theory predicts emergence of Majorana bound states is accompanied by a topological phase transition. We show experimentally in epitaxial Al/InAs Josephson junctions a transition between trivial and topological superconductivity. We observe a minimum of the critical current at the topological transition, indicating a closing and reopening of the supercondcuting gap induced in InAs, with increasing magnetic field. By embedding the Josephson junction in a phase-sensitive loop geometry, we measure a $\pi$-jump in the superconducting phase across the junction when the system is driven through the topological transition. These findings reveal a versatile two-dimensional platform for scalable topological quantum computing.