Transport signatures of Majorana bound states in superconducting hybrid structures

Abstract

In this minireview, we outline the recent experimental and theoretical progress in the creation, characterization and manipulation of Majorana bound states (MBSs) in semiconductor-superconductor (SC) hybrid structures. After an introductory overview of the broader field we specifically focus on four of our recent projects in this direction. We show that the emergence of Fano resonances in the differential conductance in a normal lead-Majorana nanowire-quantum dot setup can be exploited to determine if a single MBS is contacted by the normal lead and the quantum dot providing an experimental test of the nonlocality of MBSs. In the second project, the tunnel-coupling to two MBSs in an s-wave SC-Majorana nanowire Josephson junction (JJ) leads to a finite contribution of the MBSs to the equilibrium Josephson current probing directly the local spin-singlet contribution of the Majorana pair. We then shift our focus from MBSs forming in nanowire systems to MBSs forming in topological JJs. In a single sheet of buckled silicene with proximity induced superconductivity two local electric fields can be used to tune the junction between a topologically trivial and topologically non-trivial regime. In a Corbino geometry topological Josephson junction two MBSs harbored in Josephson vortices can rotate along the JJ and, in the course of this, will be exchanged periodically in the phase difference of the JJ. The tunneling current in a metal tip coupled to the JJ is shown to exhibit signs of the anyonic braiding phase of two MBSs.

Experimental review on Majorana zero-modes in hybrid nanowires

“…Majorana zero-modes have been intensively studied in recent years (see the research trend shown in Figure 1) owing to their potential application in fault-tolerant quantum computing. There have already been many review papers about Majoranas [1][2][3][4][5][6][7][8], mainly on Majorana theories. This review will briefly introduce recent experimental developments of one-dimensional Majorana devices, aiming to give a comprehensive overview and understanding of one-dimensional Majorana experiments.…”

Signatures of Topological Transitions in the Spin Susceptibility of Josephson Junctions

“…MBS were predicted to naturally emerge in p-wave superconductors [1,9]. However, TS can also be engineered by using a conventional s-wave superconductor in proximity to a material with nontrivial spin structure, typically provided by spin-orbit coupling (SOC) [10][11][12][13][14][15][16][17] and/or magnetic textures [18][19][20][21][22][23][24][25][26]. The proximity induced superconductivity provides the necessary particlehole symmetry, while the SOC makes possible the realization of odd-in-momentum triplet pairing.…”

Crystalline Anisotropic Topological Superconductivity in Planar Josephson Junctions

“…These states are not only of tremendous interest for fundamental research, but also because their non-Abelian statistics makes them ideal building blocks for fault tolerant quantum computation [5][6][7]. Realizations [8][9][10][11][12] of topological superconductors hosting MBS are usually sought in materials with proximity-induced s-wave pairing and a nontrivial spin structure, typically provided by spinorbit coupling (SOC) and/or magnetic textures [13][14][15][16][17][18][19][20][21][22]. In the pursuit of topological superconductivity (TS), early experimental efforts have focused mostly on onedimensional (1D) systems such as hybrid structures of superconductors and semiconductor nanowires [8][9][10][11] or atomic chains [12].…”