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TT: Fachverband Tiefe Temperaturen

TT 50: German-French Focus Session: Superconducting Junctions and Quantum Circuits

TT 50.4: Topical Talk

Mittwoch, 11. März 2026, 16:45–17:15, HSZ/0003

Second Order Topological Insulators probed with mesoscopic physics — •Sophie Gueron — Laboratoire de Physique des Solides Universite Paris-Saclay France

Second Order Topological Insulators (SOTIs) are a new family of materials, predicted to be insulating in the bulk and surfaces, and perfectly conducting along dimensional crystal hinges. Similarly to Quantum Spin Hall edges states in 2D Topological Insulators, the hinge states are expected to carry current with no dissipation and no backscattering, due to their unique spin-momentum-locked configuration, also called helicity. I will present various mesoscopic physics experiments that have uncovered the special properties of SOTIs. Firstly, experiments with superconducting contacts have led to the discovery that Bismuth was a Second Order Topological Insulator, by providing evidence of hinge states and their topological character. We have also recently extended our experiments to new SOTI materials and to non- superconducting contacts, as well as to the investigation of the current-induced spin polarization due to spin-momentum locking in the hinge states. Finally, I will present a new detection scheme to explore orbital currents in 2D materials, that has the potential to reveal persistent currents circulating at the hinges of a mesoscopic SOTI crystal.

This work is a collaborative work conducted in the Mesoscopic Physics group at Laboratoire de Physique des Solides

Keywords: topological insulators; mesoscopic physics; helical edge states; superconducting proximity effect