Magnetic breakdown and topology in the Kagome CsV3Sb5 superconductor

Researchers at Argonne National Laboratory, Hofstra University and LNCMI – Toulouse have carried out quantum oscillation measurements on high-quality single crystals of CsV₃Sb₅ (an ODC superconductor with a Kagome lattice crystal structure) using the tunnel diode oscillator technique at high magnetic fields of up to 86 T.
The high-field data reveal a sequence of magnetically broken orbitals that allow the construction of a model for the folded Fermi surface of CsV₃Sb₅ (Fig. a). They discovered large triangular sheets of the Fermi surface that make up almost half of the folded Brillouin zone (Fig. b). These sheets of the Fermi surface serve as ‘elementary blocks’ for a series of regularly spaced frequencies in the high-field oscillation spectrum (Fig. (c)).
It should be noted that these laminae have not yet been detected by angle-resolved photoemission spectroscopy (ARPES) and that they exhibit pronounced nesting. The researchers also extracted the Berry phase of the electron orbitals from the diagram of Landau levels close to the quantum limit, and therefore without the need to extrapolate, thus unambiguously establishing the non-trivial topological character of several electron bands.
These results provide valuable insights into the interaction between ODC and non-trivial topology in the recently discovered AV₃Sb₅ (A=K, Rb, Cs) lamellar Kagome metals. They also highlight the complementarity of different experimental techniques in the study of 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 reconstructed 2’2 Fermi surface of CsV3Sb5 for kz = ±π/c in repeated zones. Capital letters refer to Brillouin zone points.
(b) Enlarged diagram of x2 and v orbits.
(c) High-frequency section of the oscillation spectrum at 1.5 K on a logarithmic field scale. The k orbit corresponds to the sum of the x2 and v orbits, while the t orbit represents two triangular units of base v. Consequently, ℜ, ℒ, X contain 3, 4 and 5 triangular building blocks respectively. ∂ is the sum of the orbitals x2 and t.