Quantum Matter Seminar

Magnetic fields shift electron energies via the Zeeman effect, with
the proportionality given by the Land ́e g−factor. Conventional metals
show that the g-factor may be enhanced for small electron orbits in
the order of the inverse of the effective mass, a triumph of
single-particle theory for massive Dirac bands. However, it is not
clear how the Zeeman effect changes for correlated and topological
quantum states. In the recently discovered Kagome metal CsV3Sb5, we
determine the g-factor using spin-zeros in magnetic quantum
oscillations. The g-factor deduced is around an order of magnitude
larger than the inverse of the effective mass. This large enhancement
is visible only in magnetic breakdown orbits between conventional and
concentrated Berry curvature Fermi pockets that host large orbital
moments. Furthermore, we observe large quantum oscillations of these
small orbits in the thermal Hall effect, detect a 180-degree phase
change of the oscillations and demonstrate the phase flip as an
essential feature for QOs in the thermal transport properties. This
result will shed light on the debate of the boson versus fermion
origins of the thermal Hall effect in quantum magnets.