Quantum oscillations of thermopower in WTe2 thin films

Abstract

Few-layer ${\mathrm{WTe}}_{2}$ displays fascinating phenomena, which are believed to be closely related to the topological character of its band structure. In this work we investigate quantum oscillations of thermopower in thin ${\mathrm{WTe}}_{2}$ films. Besides four oscillation frequencies commonly observed in bulk materials, we observe an additional oscillation frequency, which has previously been attributed to topological surface states [Nat. Commun. 8, 2150 (2017)]. Through analysis of the temperature, angular, and film thickness dependence of the frequency, we conclude that it is not due to the cyclotron resonance of the surface Fermi arcs in Weyl semimetals, but rather from the bulk bands. Emergence of these bulk bands at the Fermi level is due to a band reconstruction in thin layers. They contribute to transport and may be responsible for some properties of few-layer ${\mathrm{WTe}}_{2}$.