Evidence for unfolded Fermi surfaces in the charge-density-wave state of kagome metal FeGe revealed by de Haas–van Alphen effect

The antiferromagnetic kagome lattice compound FeGe has been revealed to host an emergent charge-density-wave (CDW) state which manifests complex interplay between the spin, charge, and lattice degrees of freedom. Here, we present a comprehensive study of the de Haas–van Alphen effect by measuring torque magnetometry under magnetic fields up to 45.2 T to map Fermi surfaces in this unusual CDW state. For a field along the $c$ direction, we resolve four cyclotron orbits, with the largest one roughly corresponding to the area of the $2\times 2$ folded Brillouin zone. Three smaller orbits are characterized by light effective cyclotron masses in the range of $(0.18–0.30)m_e$. Angle-resolved measurements identify one Fermi surface segment with weak anisotropy. Combined with band structure calculations, our results suggest that features of unfolded Fermi surfaces are robust against CDW reconstruction, corroborating the unconventional effect of a short-ranged CDW on the electronic structure.