Majorana bound states in vortex lattices on iron-based superconductors

Abstract

Majorana quasi-particles may arise as zero-energy bound states in vortices on the surface of a topological insulator that is proximitized by a conventional superconductor. Such a system finds its natural realization in the iron-based superconductor FeTe${}_{0.55}$Se${}_{0.45}$ that combines bulk $s$-wave pairing with spin helical Dirac surface states, and which thus comprises the ingredients for Majorana modes in absence of an additional proximitizing superconductor. In this work, we investigate the emergence of Majorana vortex modes and lattices in such materials depending on parameters like the magnetic field strength and vortex lattice disorder. A simple 2D square lattice model here allows us to capture the basic physics of the underlying materials system. To address the problem of disordered vortex lattice, which occurs in real systems, we adopt the technique of the singular gauge transformation which we modify such that it can be used in a system with periodic boundary conditions. This approach allows us to go to larger vortex lattices than otherwise accessible, and is successful in replicating several experimental observations of Majorana vortex bound states in the FeTe${}_{0.55}$Se${}_{0.45}$ platform. Finally it can be related to a simple disordered Majorana lattice model that should be useful for further investigations on the role of interactions, and towards topological quantum computation.

arXiv comment36 + 5 pages (single column), 16 + 2 figures, comments welcome. v2: fixed typos, minor changes. Accepted for publication in the Annals of Physics special issue in memory of Phil Anderson

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• High-temperature Majorana zero modes
• Phase diagram of superconductivity in the integer quantum Hall regime
• Unveiling non-Abelian statistics of vortex Majorana bound states in iron-based superconductors using fermionic modes
• Identifying Majorana vortex modes via non-local transport
• Majorana zero modes in a magnetic and superconducting hybrid vortex
• Majorana vortex modes in spin-singlet chiral superconductors with noncollinear spin ordering: Local density of states study
• Exploring the vortex phase diagram of Bogoliubov-de Gennes disordered superconductors
• Angular momentum of vortex-core Majorana zero modes
• Coexistence of gapless and gapped vortex modes with Majorana corner states in a 2D second-order topological superconductor
• Fe${}_{1+y}$Te${}_x$Se${}_{1-x}$: a delicate and tunable Majorana material
• Scheme for braiding Majorana zero modes in vortices using an STT-matrix