Regensburg 2025 – scientific programme

Parts | Days | Selection | Search | Updates | Downloads | Help

TT: Fachverband Tiefe Temperaturen

TT 48: Topology: Majorana Physics

TT 48.2: Talk

Thursday, March 20, 2025, 15:30–15:45, H32

Interedge backscattering in time-reversal symmetric quantum spin Hall Josephson junctions — •Cajetan Heinz¹, Patrik Recher^1,2, and Fernando Dominguez^1,3 — ¹Technische Universität Braunschweig, D-38106 Braunschweig, Germany — ²Laboratory for Emerging Nanometrology, D-38106 Braunschweig, Germany — ³University of Würzburg, D-97074 Würzburg, Germany

Using standard tight-binding methods, we investigate a novel backscattering mechanism taking place on quantum spin Hall N’SNSN’ Josephson junctions in the presence of time-reversal symmetry. This extended geometry allows for the interplay between two types of Andreev bound states (ABS): the usual phase-dependent ABS localized at the edges of the central SNS junction and phase-independent ABS localized at the edges of the N’S regions. Crucially, the latter arise at discrete energies E_n and mediate a backscattering process between opposite edges on the SNS junction, yielding gap openings when both types of ABS are at resonance. In this scenario, a 4π-periodic ABS decouples from the rest of the spectrum, and thus, it can be probed preventing the emission to the quasicontinuum. Interestingly, this backscattering mechanism introduces a new length scale, determining the ratio between 4π- and 2π-periodic supercurrent contributions and distorts the superconducting quantum interference (SQI) pattern. Finally, to prove the participation of these ABS, we propose to use a magnetic flux to tune E_n to zero, resulting in the selective lifting of the fractional Josephson effect.

Keywords: Majorana; Quantum spin Hall insulator; Fractional Josephson effect; Green's functions; Tight binding