Topological Phase Transition in a Magnetic Weyl Semimetal

TL;DR

This study provides direct experimental evidence of a topological phase transition in a magnetic Weyl semimetal, revealing how magnetic order influences its electronic topology and surface states.

Contribution

It demonstrates the temperature-driven topological phase transition in Co3Sn2S2 using angle-resolved photoemission spectroscopy, highlighting the interplay between magnetism and band topology.

Findings

Disappearance of surface Fermi-arcs across Curie temperature

Recombination and annihilation of Weyl points

Clear band structure evolution observed

Abstract

Topological Weyl semimetals (TWSs) are exotic crystals possessing emergent relativistic Weyl fermions connected by unique surface Fermi-arcs (SFAs) in their electronic structures. To realize the TWS state, certain symmetry (such as the inversion or time reversal symmetry) must be broken, leading to a topological phase transition (TPT). Despite the great importance in understanding the formation of TWSs and their unusual properties, direct observation of such a TPT has been challenging. Here, using a recently discovered magnetic TWS Co3Sn2S2, we were able to systematically study its TPT with detailed temperature dependence of the electronic structures by angle-resolved photoemission spectroscopy. The TPT with drastic band structures evolution was clearly observed across the Curie temperature (TC = 177 K), including the disappearance of the characteristic SFAs and the recombination of the spin-split bands that leads to the annihilation of Weyl points with opposite chirality. These results not only reveal important insights on the interplay between the magnetism and band topology in TWSs, but also provide a new method to control their exotic physical properties.