Majorana bound states in topological insulators with hidden Dirac points

Abstract

We address the issue of whether it is possible to generate Majorana bound states at the magneticsuperconducting interface in two-dimensional topological insulators with hidden Dirac points in the spectrum. In this case, the Dirac point of edge states is located at the energies of the bulk states such that two types of states are strongly hybridized. Here, we show that well-defined Majorana bound states can be obtained even in materials with a hidden Dirac point provided that the width of the magnetic strip is chosen to be comparable with the localization length of the edge states. The obtained topological phase diagram allows one to extract precisely the position of the Dirac point in the spectrum. In addition to standard zero-bias peak features caused by Majorana bound states in transport experiments, we propose to supplement future experiments with measurements of charge and spin polarization. In particular, we demonstrate that both observables flip their signs at the topological phase transition, thus providing an independent signature of the presence of topological superconductivity. All features remain stable against substantially strong disorder.

Majorana bound states in topological insulators without a vortex

“…The gate induced splitting of subbands is also confirmed numerically (see Fig. 2) by diagonalising the Bernevig-Hughes-Zhang (BHZ) tight-binding model Hamiltonian in momentum space for a wire with a square cross-section [23][24][25][26].…”

“…Inside the topological phase (beyond the red dashed line), zero-energy MBSs (black colour) are well separated from the bulk superconducting states, whereas close to the topological phase transition line, their localization length is comparable with the wire length such that they split away from zero energy. b) The lowest part of the energy spectrum [taken along the blue dashed line of (a)], where colours indicate the BCS charge Qi = d 3 r ψi(r)| η3 |ψi(r) , with ηi the Pauli-matrices in particle-hole space [26]. Zero-energy chargeless MBSs appear in the topological phase when the condition on the localization length is fulfilled [see Eq.…”

Effects of the Vertices on the Topological Bound States in a Quasicrystalline Topological Insulator

“…From the point of view of electronics and spintronics [2][3][4][5][6], the main focus is on non-superconducting systems, and in particular on topological insulators [7][8][9][10]. For superconducting spintronics [11][12][13][14][15] and topologically protected quantum computation [16][17][18][19][20][21][22][23][24][25][26][27][28][29], even through parafermions [30][31][32][33], a prominent role is conversely played by topological superconductors [34].…”

Charge Oscillations in Quantum Spin Hall Constrictions

“…Indeed, due to the latter, 2DTIs are promising for applications in spintronics. [8][9][10] In combination with superconductors, magnetic barriers, and possibly interactions, 2DTIs are prominent candidates for realizing nonabelian anions, such as Majorana fermions [11][12][13][14][15][16][17][18][19][20] and parafermions, [21][22][23][24][25] with applications in topologically protected quantum computation. [26] These potentialities triggered intense research, leading to the discovery of several materials and heterostructures behaving as 2DTIs.…”