Unconventional Surface State Pairs in a High-Symmetry Lattice with Anti-ferromagnetic Band-folding

TL;DR

This paper demonstrates how anti-ferromagnetic multi-q structures in high-symmetry lattices can induce unconventional surface states and topological features, revealing new possibilities for surface state engineering in magnetic materials.

Contribution

It uncovers the role of anti-ferromagnetic band-folding and multi-q structures in creating novel surface states and topological features in band-inverted materials like NdBi.

Findings

Unconventional surface state pairs inside the bulk gap.

Presence of Dirac and Weyl nodes in multi-q structures.

Agreement between DFT calculations and experimental observations.

Abstract

Many complex magnetic structures in a high-symmetry lattice can arise from a superposition of well-defined magnetic wave vectors. These "multi-q" structures have garnered much attention because of interesting real-space spin textures such as skyrmions. However, the role multi-q structures play in the topology of electronic bands in momentum space has remained rather elusive. Here we show that the type-I anti-ferromagnetic 1q, 2q and 3q structures in an face-centered cubic sublattice with band inversion, such as NdBi, can induce unconventional surface state pairs inside the band-folding hybridization bulk gap. Our density functional theory calculations match well with the recent experimental observation of unconventional surface states with hole Fermi arc-like features and electron pockets below the Neel temperature. We further show that these multi-q structures have Dirac and Weyl nodes. Our work reveals the special role that band-folding from anti-ferromagnetism and multi-q structures can play in developing new types of surface states.