Researchers from Argonne National Laboratory, Hofstra University, and LNCMI – Toulouse conducted quantum oscillation measurements on high quality single crystals of CsV₃Sb₅ (a Kagome lattice cum CDW superconductor) using the tunnel diode oscillator technique in high magnetic fields up to 86 T.
The high-field data reveal a sequence of magnetic breakdown orbits that allow to construct a model for the folded Fermi surface of CsV₃Sb₅ (Fig. a). They discovered large triangular Fermi surface sheets that make up nearly half of the folded Brillouin zone (Fig. b). These Fermi surface sheets serve as “building blocks” for a series of equally spaced frequencies in the high-field oscillation spectrum Fig. (c).
Notably, these sheets have not yet been detected in angle-resolved photoemission spectroscopy (ARPES) and display pronounced nesting. The researchers also extracted the Berry phases of the electron orbits from Landau level fan diagrams near the quantum limit without the need for extrapolations, thereby unambiguously establishing the non-trivial topological character of several electron bands.
The findings provide valuable insights into the interplay of CDW and non-trivial topology in the recently discovered layered Kagome metals AV₃Sb₅ (A=K, Rb, Cs). They also highlight the complementary nature of different experimental techniques in studying complex materials.

Reference :
R. Chapai, M. Leroux, V. Oliviero, D. Vignolles, N. Bruyant, M. P. Smylie, D. Y. Chung, M. G. Kanatzidis, W.-K. Kwok, J. F. Mitchell, U. Welp, Magnetic breakdown and topology in the Kagome superconductor CsV₃Sb₅ under high magnetic field, Phys. Rev. Lett. 130, 126401 (2023).

Figure:
(a) Schematic of the 2´2 reconstructed Fermi surface of CsV₃Sb₅ for k_z = ±π/c in repeated zones. Capital letters refer to Brillouin zone points.
(b) Enlarged schematic of the x₂ and v orbits.
(c) High-frequency section of the oscillation spectrum at 1.5 K on a log field scale. The k orbit corresponds to the sum of the x₂ and v orbits, while the t orbit represents two basic triangular v units. Correspondingly, ℜ, ℒ, X contain 3, 4 and 5 triangular building blocks, respectively. ∂ is the sum of  the x₂ and t orbits.