Chiral fermion reversal in chiral crystals

TL;DR

This study demonstrates that the chirality of fermions in chiral crystals can be reversed by changing the crystal's structural chirality, confirmed through experimental observation of surface states in RhSn crystals.

Contribution

The paper provides experimental evidence linking the structural chirality of crystals to the handedness of chiral fermions, expanding understanding of topological properties in chiral materials.

Findings

Chiral fermions in RhSn are confirmed by surface Fermi arcs and helical bands.

Opposite structural chirality in RhSn and CoSi results in reversed chiral fermion handedness.

Experimental results align with theoretical band calculations.

Abstract

In materials chiral fermions such as Weyl fermions are characterized by nonzero chiral charges, which are singular points of Berry curvature in momentum space. Recently, new types of chiral fermions beyond Weyl fermions have been discovered in structurally chiral crystals CoSi, RhSi and PtAl. Here, we have synthesized RhSn single crystals, which have opposite structural chirality to the CoSi crystals we previously studied. Using angle-resolved photoemission spectroscopy, we show that the bulk electronic structures of RhSn are consistent with the band calculations and observe evident surface Fermi arcs and helical surface bands, confirming the existence of chiral fermions in RhSn. It is noteworthy that the helical surface bands of the RhSn and CoSi crystals have opposite handedness, meaning that the chiral fermions are reversed in the crystals of opposite structural chirality. Our discovery establishes a direct connection between chiral fermions in momentum space and chiral lattices in real space.