Signatures of Weyl fermion annihilation in a correlated kagome magnet

TL;DR

This study demonstrates how magnetic manipulation in a kagome semimetal causes Weyl fermions to annihilate, revealing the interplay between magnetic order and topological electronic states with potential for quantum technology applications.

Contribution

It shows that magnetic exchange collapse can induce Weyl fermion annihilation in a correlated kagome magnet, a novel mechanism for controlling topological states.

Findings

Weyl loops collapse into Dirac loops upon magnetic suppression

Topological Fermi arcs disappear in the paramagnetic phase

Weyl fermion annihilation is driven by magnetic exchange collapse

Abstract

The manipulation of topological states in quantum matter is an essential pursuit of fundamental physics and next-generation quantum technology. Here we report the magnetic manipulation of Weyl fermions in the kagome spin-orbit semimetal Co$_3$Sn$_2$S$_2$, observed by high-resolution photoemission spectroscopy. We demonstrate the exchange collapse of spin-orbit-gapped ferromagnetic Weyl loops into paramagnetic Dirac loops under suppression of the magnetic order. We further observe that topological Fermi arcs disappear in the paramagnetic phase, suggesting the annihilation of exchange-split Weyl points. Our findings indicate that magnetic exchange collapse naturally drives Weyl fermion annihilation, opening new opportunities for engineering topology under correlated order parameters.