Identifying Majorana vortex modes via non-local transport

Abstract

The combination of two-dimensional Dirac surface states with s-wave superconductivity is expected to generate localized topological Majorana zero modes in vortex cores. Putative experimental signatures of these modes have been reported for heterostructures of proximitized topological insulators, iron-based superconductors or certain transition metal dichalcogenides. Despite these efforts, the Majorana nature of the observed excitation is still under debate. We propose to identify the presence of Majorana vortex modes using a non-local transport measurement protocol originally proposed for one-dimensional settings. In the case of an isolated subgap state, the protocol provides a spatial map of the ratio of local charge-and probability-density which offers a clear distinction between Majorana and ordinary fermionic modes. We show that these distinctive features survive in the experimentally relevant case of hybridizing vortex core modes.

Conductance-matrix symmetries of multiterminal semiconductor-superconductor devices

“…In conclusion, nonlocal tunneling spectroscopy is a powerful tool that has been employed to study Andreev bound states [8,9,47] and carries signatures of Majorana bound states [7,11]. We hope that our work contributes to the interpretation of the data and expands the scope of the method by allowing access to more detailed information on the system under study.…”

“…After evaluation of the S-matrix, the conductance is calculated for the CLA case following Eqs. (9)(10)(11)(12) while in the nonlinear case, the electric charge current is calculated by numerical integration of Eq. ( 6).…”

“…Nonlocal conductance spectroscopy is the natural extension of local two-probe spectroscopy and overcomes some of its limitations. Initially used in the context of the search for signatures of Cooper-pair splitting [1][2][3][4][5], this type of measurement has been recently considered in the context of topological superconductivity (TS) [6,7] leading to its use in experiments [8,9], its inclusion in identification protocols for Majorana bound states (MBSs) in nanowires [10] and unconventional superconductors vortex cores [11], as well as for the characterization of chiral Majorana edge states in 2D TS [12] and the helical gap in 2DEGs [13]. Moreover, the same concept appears in experiments involving quantum dots to probe the non-equilibrium dynamics of quasiparticles [4,14].…”