Identifying Majorana bound states at quantum spin Hall edges using a metallic probe

Abstract

We study the conductance afforded by a normal-metal probe which is directly contacting the helical edge modes of a quantum spin Hall insulator (QSHI). We show a 2e 2 /h conductance peak in QSHI-based superconductor-ferromagnet hybrids due to the formation of a single Majorana bound state (MBS). In a corresponding Josephson junction hosting a pair of MBSs, a 4e 2 /h conductance peak is found. The conductance quantization is robust to changes of the relevant system parameters and, remarkably, remains unaltered with increasing the distance between probe and MBSs. Our findings can therefore provide an effective way to detect the existence of MBSs in QSHI systems.

Phase-tunable electron transport assisted by odd-frequency Cooper pairs in topological Josephson junctions

“…Under general conditions, we find finite local pair amplitudes with ESE (OTE) symmetry in all regions of the junction, denoted here as F r,E(O) , respectively. While the ESE symmetry is in the spin-singlet state of the parent superconductor, the OTE symmetry is in the mixed spin-triplet state and emerges due to the strong spinmomentum locking in 2DTI edges [14,20,56,64,65]. The existence of these two pair symmetries in both the N and S regions is determined by the scattering processes at the junction interfaces, which also introduce a strong dependence on the superconducting phase difference φ.…”