Geometric dependence of Nb-Bi${_2}$Te${_3}$-Nb topological Josephson junction transport parameters

TL;DR

This study investigates how geometric factors influence transport parameters in Nb-Bi2Te3-Nb topological Josephson junctions, revealing that observed anomalies are due to geometry rather than Majorana states.

Contribution

The paper demonstrates that geometric effects, not Majorana bound states, explain anomalous scaling in topological Josephson junctions.

Findings

Anomalous scaling explained by geometric effects

Flux focusing impacts critical current modulation

Bulk conductivity shunt influences transport parameters

Abstract

Superconductor-topological insulator-superconductor Josephson junctions have been fabricated in order to study the width dependence of the critical current, normal state resistance and flux periodicity of the critical current modulation in an external field. Previous literature reports suggest anomalous scaling in topological junctions due to the presence of Majorana bound states. However, for most realised devices, one would expect that trivial $2\pi$-periodic Andreev levels dominate transport. We also observe anomalous scaling behaviour of junction parameters, but the scaling can be well explained by mere geometric effects, such as the parallel bulk conductivity shunt and flux focusing.