Quasiparticles and optical conductivity in the mixed state of Weyl superconductors with unconventional pairing

TL;DR

This paper studies quasiparticle excitations and optical responses in Weyl superconductors with unconventional pairing, revealing distinct Landau level structures and optical signatures for different pairing symmetries.

Contribution

It uncovers how unconventional pairing affects Landau levels and optical conductivity in Weyl superconductors, highlighting differences between d-wave and p-wave pairings.

Findings

d-wave pairing induces flat Dirac Landau levels

p-wave pairing shows dispersive Landau levels with a protected zero mode

distinct magneto-optical conductivity signatures for different pairings

Abstract

Previous investigations have revealed that the Weyl superconductor (WeylSC), realized in a superconductor-topological insulator heterostructure, can exhibit the Landau levels (LLs) of Bogoliubov quasiparticles in the presence of a vortex lattice. Here, we investigate the low-energy quasiparticle (QP) excitations in the mixed state of heterostructure WeylSCs with unconventional pairing. We find that the spin-singlet $d$-wave pairing induces flat Dirac-LLs of Bogoliubov QPs, whereas the excitation spectra for the spin-triplet chiral $p$-wave pairing show noticeable dispersion, except for the chiral symmetry-protected, dispersionless, zeroth Landau level (ZLL). Distinct QP excitations in the vortex lattice of WeylSCs result in different optical responses, which are manifested as characteristic magneto-optical conductivity curves. We also show that, compared to the topologically protected, charge-neutral, localized Majorana zero mode (MZM), the chiral symmetry-protected ZLL is non-charge-neutral and delocalized. Both of these zero modes may be observed in the mixed state of a heterostructure topological superconductor.