Special CPM Seminar

Phase fingerprint of topological transition in Josephson Junctions

Javad Shabani

New York University

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 superconducting gap induced in InAs, with increasing magnetic field. By embedding the Josephson junction in a phase-sensitive loop geometry, we measure a π-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.