Topological Electronic Structure Evolution with Symmetry Breaking Spin Reorientation in (Fe$_{1-x}$Co$_{x}$)Sn

TL;DR

This study investigates how magnetic symmetry breaking influences the topological electronic structure in (Fe$_{1-x}$Co$_{x}$)Sn, revealing a Dirac gap in the axial phase and surface band shifts linked to magnetic disorder.

Contribution

It provides experimental and theoretical insights into the interplay between magnetic phases and topological electronic structures in a kagome lattice system.

Findings

A Dirac gap appears in the axial magnetic phase at low temperature.

Surface bands shift in energy with magnetic disorder during measurements.

No bulk gap opening observed across the magnetic phase transition.

Abstract

Topological materials hosting kagome lattices have drawn considerable attention due to the interplay between topology, magnetism, and electronic correlations. The (Fe$_{1-x}$Co$_x$)Sn system not only hosts a kagome lattice but has a tunable symmetry breaking magnetic moment with temperature and doping. In this study, angle resolved photoemission spectroscopy and first principles calculations are used to investigate the interplay between the topological electronic structure and varying magnetic moment from the planar to axial antiferromagnetic phases. A theoretically predicted gap at the Dirac point is revealed in the low temperature axial phase but no gap opening is observed across a temperature dependent magnetic phase transition. However, topological surface bands are observed to shift in energy as the surface magnetic moment is reduced or becomes disordered over time during experimental measurements. The shifting surface bands may preclude the determination of a temperature dependent bulk gap but highlights the intricate connections between magnetism and topology with a surface/bulk dichotomy that can affect material properties and their interrogation.