Observation of a two dimensional Fermi surface in TaAs

Three dimensional Weyl semimetals are characterized by bulk quasiparticles that behave as massless, linearly dispersing Weyl fermions and have excited physicists with their unique topological properties and potential for applications. TaAs, one such Weyl material, has been shown to host exotic phenomena such as the chiral anomaly and Fermi arc surface states. Here, we report transport measurements indicating the presence of an additional, two-dimensional Fermi surface in TaAs. High quality samples of TaAs show pronounced Shubnikov de Haas oscillations beginning at fields below 1T. The low-field oscillations are in close agreement with what has been reported in the literature. At intermediate fields, however, an additional, high-frequency oscillation is observed. This new oscillation disperses in angle in a manner consistent with a two-dimensional state, indicating the presence of a previously unobserved Fermi surface.