Multiband s-wave topological superconductors: role of dimensionality and magnetic field response

Abstract

We further investigate a class of time-reversal-invariant two-band s-wave topological superconductors introduced in Phys. Rev. Lett. 108, 036803 (2012). We show how, in the presence of time-reversal symmetry, Z_2 invariants that distinguish between trivial and non-trivial quantum phases can be constructed by considering only one of the Kramers' sectors in which the Hamiltonian decouples into. We find that the main features identified in our original 2D setting remain qualitatively unchanged in 1D and 3D, with non-trivial topological superconducting phases supporting an odd number of Kramers' pairs of helical Majorana modes on each boundary, as long as the required $\pi$ phase difference between gaps is maintained. We also analyze the consequences of time-reversal symmetry-breaking either due to the presence of an applied or impurity magnetic field or to a deviation from the intended phase matching between the superconducting gaps. We demonstrate how the relevant notion of topological invariance must be modified when time-reversal symmetry is broken, and how both the persistence of gapless Majorana modes and their robustness properties depend in general upon the way in which the original Hamiltonian is perturbed. Interestingly, a topological quantum phase transition between helical and chiral superconducting phases can be induced by suitably tuning a Zeeman field in conjunction with a phase mismatch between the gaps. Recent experiments in doped semiconducting crystals, of potential relevance to the proposed model, and possible candidate material realizations in superconductors with $s_{\pm }$ pairing symmetry are discussed.

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• Magnetic Field Response and Chiral Symmetry of Time Reversal Invariant Topological Superconductors
• Band hybridization induced odd-frequency pairing in multiband superconductors
• Topological Properties of Time Reversal Symmetric Kitaev Chain and Applications to Organic Superconductors
• Exact zero modes in twisted Kitaev chains
• Squaring the fermion: The threefold way and the fate of zero modes
• Majorana Flat Bands in s-Wave Gapless Topological Superconductors
• Generalization of Bloch's theorem for arbitrary boundary conditions: Interfaces and topological surface band structure
• Dynamical generation of Floquet Majorana flat bands in s-wave superconductors
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• Phase diagram of a model for topological superconducting wires
• Hidden Symmetry Decoupling of Majorana Fermions
• Andreev spectroscopy of Majorana states in topological superconductors with multipocket Fermi surfaces
• Nested Defects on the Boundary of Topological Superconductors
• Topological transitions in two-dimensional Floquet superconductors
• Equivalence of topological mirror and chiral superconductivity in one dimension
• Tunable zero modes and quantum interferences in flat-band topological insulators
• A theorem regarding families of topologically non-trivial fermionic systems
• Realizing Majorana Kramers pairs in two-channel InAs-Al nanowires with highly misaligned electric fields