Majorana surface modes of nodal topological pairings in spin-$\frac{3}{2}$ semi-metals

TL;DR

This paper explores topological superconductivity in spin-3/2 systems, specifically in half-Heusler compounds, revealing Majorana surface modes with unique spectral features and potential experimental signatures.

Contribution

It systematically analyzes topological pairing structures in spin-3/2 systems with cubic symmetry, identifying Majorana surface states and their experimental signatures.

Findings

Majorana surface modes with flat and cubic dispersion.

Surface states detectable via tunneling experiments.

Topological structures specific to spin-3/2 systems.

Abstract

Multi-component electronic systems can appear in solid state systems with active orbital band structures. They exhibit richer structures of topological superconductivity beyond the conventional scenarios of spin singlet and triplet pairings in spin-$\frac{1}{2}$ systems. Examples include the half-Heusler compounds RPtBi series (R for a rare earth element), whose electronic structures are described by the effective Luttinger-Kohn model with spin-$\frac{3}{2}$ fermions exhibiting strong spin-orbit coupling and band conversion. Recent experiments provide evidence to unconventional superconductivity in the YPtBi material with nodal spin-septet pairing. We systematically study topological pairing structures in spin-$\frac{3}{2}$ systems with cubic group symmetries and calculate surface Majorana spectra, which exhibit both the zero energy flat band and the cubic dispersion. The signatures of these surface states in the quasi-particle interference patterns are studied, which can be tested in future tunneling experiments.