Signatures of Higher Order Topology in S-Bi-S Junctions

Perfect 3D pure bismuth is a very intriguing material, but its electronic states were considered topologically trivial until recent works suggesting that it may host 1D helical states on some hinges. Indeed, bismuth fits in the new class of material called "second order topological insulator" (SOTI).

Our group participated in the discovery of this first SOTI [1] by controling the phase bias on a single-crystalline bismuth nanowires coupled to superconducting contacts. We demonstrated that supercurrent is carried by narrow ballistic channels, both in low frequency [2] and high frequency experiments [3].

In this talk, I will present ongoing works on ring-shaped bismuth samples probed with low frequency superconducting switching statistics analysis. This upgraded method provides additionnal informations on the supercurrent-carrying states, and tackles perfect Andreev levels crossing resolution and parity lifetime.

[1] F. Schindler et al., Nat. Phys. 9, 918-924 (2018).
[2] A. Murani et al., Nat. Comm. 8, 15941 (2017).
[3] A. Murani et al., Phys. Rev. Lett. 122, 076802 (2019).