Topological Splitting of Sondheimer Oscillations in Thin-Film Weyl Semimetals

We discuss topological effects on Sondheimer oscillations in the magnetoresistance of thin-film Weyl semimetals. The Sondheimer oscillations are periodic in magnetic field and originate from the commensurability between the film thickness and the cyclotron-orbit pitch. Using Boltzmann transport theory, we investigate the effects of Berry curvature and orbital magnetic moment on the oscillations. We find that the Sondheimer oscillations split into two branches with different frequencies and that each branch becomes chirped because its frequency depends on magnetic field. These features originate from the orbital-Zeeman-induced deformation of the Fermi surface. The same mechanism also applies to Dirac semimetals.