Speaker
Description
We theoretically investigate Weyl superconductivity in quasicrystals. Weyl superconductivity is a topological phase in three-dimensional crystals with topologically protected point nodes in the Brillouin zone called Weyl nodes, at which the Chern number changes its value [1]. Quasicrystals (QCs) are materials whose structure is aperiodic with a long-range order. As they lack translational symmetry and hence the Brillouin zone, the Chern number cannot be defined for their topological characterization. Accordingly, a theory of Weyl superconductivity has not been established for QCs in spite of recent extensive studies on quasicrystalline topological phases.
We extend the concept of Weyl superconductors to periodically stacked, two-dimensional quasicrystalline topological superconductors. To visualize this new concept, we examine quasicrystalline Weyl superconductivity realized in layered Ammann-Beenker and Penrose quasicrystals with spin-orbit coupling under an external magnetic field. We calculate the Bott index in real space as a reliable topological invariant [2] to characterize quasicrystalline Weyl nodes [3]. In the presence of surface boundaries, zero-energy Majorana surface modes emerge between two Weyl nodes in momentum space corresponding to the stacking direction. We find that the Majorana zero modes are decomposed into an infinite number of components resolved in momentum in the direction along surfaces within each layer. The distribution forms quasiperiodic arcs, which we call aperiodic Majorana arcs. We show that, in layered Ammann-Beenker (Penrose) quasicrystals, the position of the aperiodic Majorana arcs is characterized by the silver (golden) ratio associated with the quasicrystalline structure.
[1] T. Meng and L. Balents, Phys. Rev. B 86, 054504 (2012).
[2] R. Ghadimi, T. Sugimoto, K. Tanaka, and T. Tohyama, Phys. Rev. B 104, 144511 (2021).
[3] A. G. e Fonseca et al., Phys. Rev. B 108, L121109 (2023).
| Keyword-1 | Weyl superconductivity |
|---|---|
| Keyword-2 | Quasicrystals |
| Keyword-3 | Majorana quasiparticle |
