Anomalous flux periodicity in proximitised quantum spin Hall constrictions. (1st May 2022)

• Record Type: Journal Article
• Authors: Vigliotti, Lucia; Calzona, Alessio; Trauzettel, Björn; Sassetti, Maura; Ziani, Niccolò Traverso
• Is Part Of: New journal of physics. Volume 24:Number 5(2022)
• Publication Date: 2022-05-01
• Subjects: edge states -- Josephson junctions -- topological insulators -- helical constrictions -- quantum interference -- 4π-periodicity; Physics -- Periodicals; Physics; Periodicals; 530.05
• DOI: 10.1088/1367-2630/ac643b
• Languages: English
• ISSNs: 1367-2630

Abstract

Abstract: We theoretically analyse a long constriction between the helical edge states of a two-dimensional topological insulator. The constriction is laterally tunnel-coupled to two superconductors and a magnetic field is applied perpendicularly to the plane of the two-dimensional topological insulator. The Josephson current is calculated analytically up to second order in the tunnel coupling both in the absence and in the presence of a bias (DC and AC Josephson currents). We show that in both cases the current acquires an anomalous 4 π -periodicity with respect to the magnetic flux that is absent if the two edges are not tunnel-coupled to each other. The result, that provides at the same time a characterisation of the device and a possible experimental signature of the coupling between the edges, is stable against temperature. The processes responsible for the anomalous 4 π -periodicity are the ones where, within the constriction, one of the two electrons forming a Cooper pair tunnels between the two edges.