Topological phase transitions in strongly correlated systems: application to Co$_3$Sn$_2$S$_2$

TL;DR

This paper investigates the topological phase transition in the strongly correlated ferromagnetic compound Co$_3$Sn$_2$S$_2$, highlighting the change from Weyl semimetal to a non-magnetic state and its relation to magnetic and topological properties.

Contribution

It provides a theoretical description of the topological transition in Co$_3$Sn$_2$S$_2$ using slave fermion representation and explores the coexistence of topology and ferromagnetism.

Findings

Topological invariant changes during the transition.

Transition from ferromagnetic to paramagnetic state.

Transformation of the minority Fermi surface from ghost to real.

Abstract

The topological transition in the strongly correlated half-metallic ferromagnetic compound Co$_3$Sn$_2$S$_2$ from Weyl semimetal (including chiral massless fermions) to a non-magnetic state is treated. This transition goes with a change in topological invariant, and is accompanied by a non-topological transition from saturated ferromagnetic to paramagnetic state, the minority Fermi surface being transformed from ghost (hidden) to real. A corresponding description is given in terms of slave fermion representation for the effective narrow-band Hubbard model. The system Co$_3$Sn$_2$S$_2$ provides a bright example of coexistence of non-trivial topology and strong low-dimensional ferromagnetism. A comparison is performed with other compounds where frustrations result in formation of a correlated paramagnetic state.